Webmin does not start: Only Reference pam_unix(webmin:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= r

I am having a problem starting webmin and the could not find a solution so far.
The error I am getting is “pam_unix(webmin:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= r”

Loaded: loaded (/etc/init.d/webmin; generated)
Active: failed (Result: exit-code) since Sat 2019-11-16 20:15:05 CET; 12s ago
Docs: man:systemd-sysv-generator(8)
Process: 9779 ExecStart=/etc/init.d/webmin start (code=exited, status=2)

Nov 16 20:15:03 hostname systemd[1]: Starting LSB: web-based administration interface for Unix systems…
Nov 16 20:15:03 hostname perl[9780]: pam_unix(webmin:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= r
Nov 16 20:15:05 hostname systemd[1]: webmin.service: Control process exited, code=exited status=2
Nov 16 20:15:05 hostname systemd[1]: webmin.service: Failed with result ‘exit-code’.
Nov 16 20:15:05 hostname systemd[1]: Failed to start LSB: web-based administration interface for Unix systems.

the miniserv.error shows no logs and there is no additional information that can point me to a probable cause. Anyone knows how to receive more logs from a failure to start?
(Ubuntu 18.x)
P.S Found some similar cases in forum, related to SSL but this does not seem to be my case