Cannot login to chef via web ui - problem with erchef?

I am trying to log into the chef server via the web ui (https://chefserver.com/users/login)

The login takes a long time after which time, I get the following (generic) error message:

We're sorry, but something went wrong.

Displayed on the

https://chefserver.com/users/login_exec page.

The contents of the relevant log file are as follows:

/var/log/chef-server/erchef/crash.log:

Offender:   [{pid,<0.315.0>},{name,connection},{mfa,{amqp_network_connection,start_link,[{amqp_params,<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>,<<"/chef">>,{127,0,0,1},8672,0,0,0,none,[]},<0.314.0>,#Fun<amqp_connection_sup.0.67288451>]}},{restart_type,intrinsic},{shutdown,brutal_kill},{child_type,worker}]

    2019-09-27 10:01:07 =SUPERVISOR REPORT====
     Supervisor: {<0.313.0>,amqp_connection_sup}
     Context:    shutdown
     Reason:     reached_max_restart_intensity
     Offender:   [{pid,<0.315.0>},{name,connection},{mfa,{amqp_network_connection,start_link,[{amqp_params,<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>,<<"/chef">>,{127,0,0,1},8672,0,0,0,none,[]},<0.314.0>,#Fun<amqp_connection_sup.0.67288451>]}},{restart_type,intrinsic},{shutdown,brutal_kill},{child_type,worker}]

    2019-09-27 10:01:07 =ERROR REPORT====
    ["Could not connect, scheduling reconnect.",{error,{{error,{badmatch,{error,{auth_failure_likely,{econnrefused,{gen_server,call,[<0.315.0>,connect,infinity]}}}}},[{bunny_util,connect,1,[{file,"src/bunny_util.erl"},{line,191}]},{gen_bunny_mon,do_connect,3,[{file,"src/gen_bunny_mon.erl"},{line,192}]},{gen_bunny_mon,handle_info,2,[{file,"src/gen_bunny_mon.erl"},{line,134}]},{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,607}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]},{connection_info,{network,{127,0,0,1},8672,{<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>},<<"/chef">>}}}}]

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/var/log/chef-server/erchef/current:

2019-09-27_10:01:07.65678
2019-09-27_10:01:07.69045 [error] gen_server <0.315.0> terminated with reason: econnrefused
2019-09-27_10:01:07.69915 [error] CRASH REPORT Process <0.315.0> with 0 neighbours exited with reason: econnrefused in gen_server:terminate/6 line 747
2019-09-27_10:01:07.70837 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason econnrefused in context child_terminated
2019-09-27_10:01:07.71568 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason reached_max_restart_intensity in context shutdown
2019-09-27_10:01:07.73472 [error] "Could not connect, scheduling reconnect.", error: {{error,{badmatch,{error,{auth_failure_likely,{econnrefused,{gen_server,call,[<0.315.0>,connect,infinity]}}}}},[{bunny_util,connect,1,[{file,"src/bunny_util.erl"},{line,191}]},{gen_bunny_mon,do_connect,3,[{file,"src/gen_bunny_mon.erl"},{line,192}]},{gen_bunny_mon,handle_info,2,[{file,"src/gen_bunny_mon.erl"},{line,134}]},{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,607}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]},{connection_info,{network,{127,0,0,1},8672,{<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>},<<"/chef">>}}}
2019-09-27_10:01:08.68549 [info] Negotiated maximums: (Channel = 0, Frame = 131072, Heartbeat = 0)
2019-09-27_10:01:08.68552
2019-09-27_10:01:08.69512 [info] Application chef_wm started on node 'erchef@127.0.0.1'
2019-09-27_10:01:08.69526 [info] Application opscoderl_wm started on node 'erchef@127.0.0.1'

/var/log/chef-server/erchef/erchef.log:

2019-09-27 10:01:07.622 [error] gen_server <0.315.0> terminated with reason: econnrefused
2019-09-27 10:01:07.622 [error] CRASH REPORT Process <0.315.0> with 0 neighbours exited with reason: econnrefused in gen_server:terminate/6 line 747
2019-09-27 10:01:07.622 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason econnrefused in context child_terminated
2019-09-27 10:01:07.622 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason reached_max_restart_intensity in context shutdown
2019-09-27 10:01:07.623 [error] "Could not connect, scheduling reconnect.", error: {{error,{badmatch,{error,{auth_failure_likely,{econnrefused,{gen_server,call,[<0.315.0>,connect,infinity]}}}}},[{bunny_util,connect,1,[{file,"src/bunny_util.erl"},{line,191}]},{gen_bunny_mon,do_connect,3,[{file,"src/gen_bunny_mon.erl"},{line,192}]},{gen_bunny_mon,handle_info,2,[{file,"src/gen_bunny_mon.erl"},{line,134}]},{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,607}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]},{connection_info,{network,{127,0,0,1},8672,{<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>},<<"/chef">>}}}
2019-09-27 10:01:08.685 [info] Negotiated maximums: (Channel = 0, Frame = 131072, Heartbeat = 0)

2019-09-27 10:01:08.694 [info] Application chef_wm started on node 'erchef@127.0.0.1'
2019-09-27 10:01:08.695 [info] Application opscoderl_wm started on node 'erchef@127.0.0.1'

/var/log/chef-server/nginx/access.log:

PuTTY==> /var/log/chef-server/erchef/erchef.log <==

2019-09-27 10:01:07.622 [error] gen_server <0.315.0> terminated with reason: econnrefused
2019-09-27 10:01:07.622 [error] CRASH REPORT Process <0.315.0> with 0 neighbours exited with reason: econnrefused in gen_server:terminate/6 line 747
2019-09-27 10:01:07.622 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason econnrefused in context child_terminated
2019-09-27 10:01:07.622 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason reached_max_restart_intensity in context shutdown
2019-09-27 10:01:07.623 [error] "Could not connect, scheduling reconnect.", error: {{error,{badmatch,{error,{auth_failure_likely,{econnrefused,{gen_server,call,[<0.315.0>,connect,infinity]}}}}},[{bunny_util,connect,1,[{file,"src/bunny_util.erl"},{line,191}]},{gen_bunny_mon,do_connect,3,[{file,"src/gen_bunny_mon.erl"},{line,192}]},{gen_bunny_mon,handle_info,2,[{file,"src/gen_bunny_mon.erl"},{line,134}]},{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,607}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]},{connection_info,{network,{127,0,0,1},8672,{<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>},<<"/chef">>}}}
2019-09-27 10:01:08.685 [info] Negotiated maximums: (Channel = 0, Frame = 131072, Heartbeat = 0)

2019-09-27 10:01:08.694 [info] Application chef_wm started on node 'erchef@127.0.0.1'
2019-09-27 10:01:08.695 [info] Application opscoderl_wm started on node 'erchef@127.0.0.1'
==> /var/log/chef-server/erchef/crash.log <==
     Offender:   [{pid,<0.315.0>},{name,connection},{mfa,{amqp_network_connection,start_link,[{amqp_params,<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>,<<"/chef">>,{127,0,0,1},8672,0,0,0,none,[]},<0.314.0>,#Fun<amqp_connection_sup.0.67288451>]}},{restart_type,intrinsic},{shutdown,brutal_kill},{child_type,worker}]

/var/log/chef-server/erchef/crash.log:

    Offender:   [{pid,<0.315.0>},{name,connection},{mfa,{amqp_network_connection,start_link,[{amqp_params,<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>,<<"/chef">>,{127,0,0,1},8672,0,0,0,none,[]},<0.314.0>,#Fun<amqp_connection_sup.0.67288451>]}},{restart_type,intrinsic},{shutdown,brutal_kill},{child_type,worker}]

2019-09-27 10:01:07 =SUPERVISOR REPORT====
     Supervisor: {<0.313.0>,amqp_connection_sup}
     Context:    shutdown
     Reason:     reached_max_restart_intensity
     Offender:   [{pid,<0.315.0>},{name,connection},{mfa,{amqp_network_connection,start_link,[{amqp_params,<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>,<<"/chef">>,{127,0,0,1},8672,0,0,0,none,[]},<0.314.0>,#Fun<amqp_connection_sup.0.67288451>]}},{restart_type,intrinsic},{shutdown,brutal_kill},{child_type,worker}]

2019-09-27 10:01:07 =ERROR REPORT====
["Could not connect, scheduling reconnect.",{error,{{error,{badmatch,{error,{auth_failure_likely,{econnrefused,{gen_server,call,[<0.315.0>,connect,infinity]}}}}},[{bunny_util,connect,1,[{file,"src/bunny_util.erl"},{line,191}]},{gen_bunny_mon,do_connect,3,[{file,"src/gen_bunny_mon.erl"},{line,192}]},{gen_bunny_mon,handle_info,2,[{file,"src/gen_bunny_mon.erl"},{line,134}]},{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,607}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]},{connection_info,{network,{127,0,0,1},8672,{<<"chef">>,<<"b5e8a22a441b6097485e2df04b7577b46150bcd4cebfb5599bcc6f3a78cfbf93f71066f4082833a992e4f403f16f1ba98635">>},<<"/chef">>}}}}]
==> /var/log/chef-server/erchef/current <==
2019-09-27_10:01:07.65678
2019-09-27_10:01:07.69045 [error] gen_server <0.315.0> terminated with reason: econnrefused
2019-09-27_10:01:07.69915 [error] CRASH REPORT Process <0.315.0> with 0 neighbours exited with reason: econnrefused in gen_server:terminate/6 line 747
2019-09-27_10:01:07.70837 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason econnrefused in context child_terminated
2019-09-27_10:01:07.71568 [error] Supervisor {<0.313.0>,amqp_connection_sup} had child at module undefined at <0.315.0> exit with reason reached_max_restart_intensity in context shutdown

All of the other log files (chef-server-webui, rabbitmq, chef-expander, chef-solr, bookshelf, nginx) appear to terminate 'normally'.

Thanks,
Sean