Can't see added clients

[yubiuser]

Client Menu error on Web UI

Somehow your database got corrupted (power outages?). You could try to repair it (/etc/pihole/pihole-ftl.db) Or (might be easier) delete/remove it and start fresh over: sudo service pihole-FTL stop sudo mv /etc/pihole/pihole-FTL.db /etc/pihole/pihole-FTL_old.db sudo service pihole-FTL start

Exchange pihole-FTL.db with gravity.db if you try to repair it.

For the reason, see here (different error, but likely same underlying issue)

Web interface not working

That unit file has been corrupted, it's just containing gibberish now. You may get lucky by replacing it with the normal content (click for details). But files don't change their content by themselves, there has to be a reason why that file has been corrupted. Two common causes would be an insufficient power supply or a defective sd card that's nearing its end of life. There's also a chance this happened during a sudden power loss or by just pulling the plug on your Pi-hole machine. You sho…