So before I used Cloudflare I was able to access both the main site and forum. However, after setting up Cloudflare, I can only reach the main site. I get an error on the forum that says: DNS_PROBE_FINISHED_NXDOMAIN
I searched several articles on this and tried to add a CNAME eventually but it was already there, so I don’t know what I am supposed to do now.
The first issue is, you havent created a DNS record for “www.forum”, so it cant resolve in the first place.
Though, even if you created that record, it wouldnt work on HTTPS → Subdomain too deep. You’d first need to purchase a $10/month dedicated certificate from Cloudflare.