today one of our subdomains went out of reach with error DNS_PROBE_FINISHED_NXDOMAIN
I checked the DNS and I noticed the CNAME is not resolving to our Heroku service.
the WWW CNAME is working correctly but other subdomains CNAME does not return anything in DNS checker. I made some other test CNAME to test if they work but the result is same.
Note that CNAME is not proxied.
Do you guys have any ideas what could happen all of a sudden?