DoH with Quad9 not Working

Hello everyone :smile:

I am using OpenWrt 21.02.2 with TP-Link Archer C20 V5.

For some reason one day DoH with Quad9 just stopped working.
I am using https-dns-proxy with both dns resolvers set to Quad9 (recommended). BUT DNS resolution just DOES NOT work with ANY quad9 servers. Cloudflare, Google etc work with DoH. The problem is only with Quad9.
I have already checked the config file for https-dns-proxy and the config for quad9 dns ipv4 address and DoH url all match up with the official documentation on quad9 website.

Any ideas on fixing it ? Ask for more information if necessary ! Thanks :blush: