Without some diagnostic data from a tool like dig it is difficult for the community to know what happened. The documentation indicates that DNS updates should propagate in about 5 minutes, but depending on local DNS caching this may take longer.
One thing to be careful of is to not ‘pollute’ a DNS cache with a negative TTL. If you query for a DNS record before the record is created, then a DNS cache might cache the negative result for much longer. The minimum TTL I have seen in Cloudflare SOA records is either 300 or 3600 seconds (5 or 60 minutes).