Issue Transport endpoint is not connected

[Kais72]

Server operating system version

Ubuntu 22.04.2 LTS

Plesk version and microupdate number

Plesk Obsidian Versión 18.0.55

Hello community,
I'm getting this error message when I access to my plesk panel (see attached).
Plesk itself and my websites are getting 504 errors or they are unreacheable.
Running "systemctl status apache2.service" results in "Failed to get properties: Transport endpoint is not connected"

Thanks in advance.