Quad9 DNS randomly stopped working

I have been using Quad9 for my DNS, setup at the router level, for months without issue. Today, I woke up and the internet wasn't working, and as the one in the house who self-hosts a couple things on an old laptop and thus tinkers with the router, I was the one my roommates looked at in a panic.

I figured I'd just do a factory reset, and it worked! And then stopped working when I changed the DNS from my ISP's servers to Quad9's. I can't even ping their servers from my home network.

Could my home IP have been banned from Quad9 for some reason? I truly can't imagine why.

EDIT: Update if anyone cares, it works now. I assume it was a problem somewhere between my network and Quad9's servers, since I didn't change any configurations to make it work.