Oracle XE 18c with Apex 19 on top has got a default password expiration setup and user profile setup which one day simply ends up as a closed down service. Only place to find a decent log is webservers access log (if you are lucky enough to have it).
"Common user" is really unhelpfull, basically your APEX_PUBLIC_USER account password has expired. Hopefully you recall original password, otherwise you will have to change password hashes in dads.conf.
SELECT username, account_status FROM dba_users WHERE ACCOUNT_STATUS LIKE '%EXPIRED%';
ALTER USER APEX_PUBLIC_USER IDENTIFIED BY yourpassword (dont use SEMICOLON; - use new line)
alter user APEX_PUBLIC_USER account unlock;
In case you still stuck, somehow Apex 19 likes anonymous account being unlocked: