It seems to say `License is not available, authentication is not possible.
$ tail /var/log/kibana/kibana.log
... snip ...
{"type": "log","@timestamp": "2021-05-31T10:24:47+09:00", "tags":["error", "plugins", "security", "authentication"], "pid": "28000"," message": "License is not available, authentication is not possible."}
... snip ...
Do you have any other clues?