503 Service Unavailable on GCP

My pleasure. Glad to hear you got things working.

If you run into issues in the future tailing the error logs for the control panel or litespeed/openlitespeed is the best way to debug.

For example:
tail -f /usr/local/lscp/cyberpanel/logs/error.log
or
tail -f /usr/local/lsws/logs/error.log

More helpful log files details.
Cyberpanel Control Panel Accesslog
/usr/local/lscp/cyberpanel/logs/access.log

Cyberpanel Control Panel errorlog
/usr/local/lscp/cyberpanel/logs/error.log

Cyberpanel Control Panel stderr.log
/usr/local/lscp/cyberpanel/logs/stderr.log

Cyberpanel Control Panel logs and rotated logs.
/usr/local/lscp/logs/

Litespeed/Openlitespeed

/usr/local/lsws/logs/error.log
/usr/local/lsws/logs/access.log
/usr/local/lsws/logs/auditmodsec.log

See
https://www.litespeedtech.com/support/wiki/doku.php/litespeed_wiki:php:503-errors
https://openlitespeed.org/kb/troubleshooting-php-503-errors/

https://docs.cyberpanel.net/doku.php?id=start