No Access to DNS servers

My home network do not have access to NextDNS (dns) servers. It was working until ~30 minutes ago. Both addresses are not responding. I had to switch back to my default internet provider DNS servers :(

I was trying to run https://nextdns.io/diag but at the end it fails with the error:

Post unsuccessful: status 400
{"error":"0: instance requires property \"PrimaryTraceroute\"\n1: instance requires property \"SecondaryTraceroute\"\n"}

Looks like ipv6 version of nextdns dns servers are working, only ipv4 version is not responding.
Unfortunately my router do not allow to set ipv6 version.

Any ideas what's going on?