Pi-hole suddenly stops working. DNS service not running

I've been using pi-hole on my Raspi zero 2 and a FRITZ!Box 6660 for about a year without any problems. Today I suddenly couldn't access any websites and several restarts of the router and raspi didn't help either. In the meantime I can at least get back into the admin panel of pi hole. It says that the DNS service is not running (see picture). What is going on there? Unfortunately I can't upload a log because the pc is offline now.

Is the sd card perhaps defective?

I'm looking forward for help.

Thanks a lot!

The whole pihole folder under /etc was deleted. I’ve no idea why. i've reinstalled pi-hole and now it's working again. Very strange!