Webadmin cannot access Dashboard; reinstalled/configured Lighttpd to no avail

Expected Behaviour:

Pihole is up and running, Websites being blocked, when attempting to login to Admin a successful login will revert back to index.php (cannot access dashboard)

I have tried the following:
1: Repaired pihole pihole -r
2: uninstalled/reinstalled/reconfigured lighttpd

Actual Behaviour:

redirected to index.php on Webadmin, cannot get to dashboard

Debug Token:

https://tricorder.pi-hole.net/3eh5IRo5/

From your debug log, it seems there is a Docker installation on your Pi-hole host machine.
Are you running a dockered Pi-hole?

Unrelated to your issue, I've noticed that you have configured quite a few ineffective regex blocks like
^https?://([A-Za-z0-9.-]*\.)?clicks\.beap\.bc\.yahoo\.com/
Rather than domains, those are trying to match URLs, which Pi-hole as a DNS resolver will never see.
You should either remove or change those to match domains (i.e. drop leading protocols and trailing paths as applicable).