Your subdomain is not resolving
The records are saved at your DNS provider and the subdomain still is not answering. These are the causes in the order they usually turn out to be the answer. For the records themselves, see Subdomain setup.
The wrong record type was added
Section titled “The wrong record type was added”Datahash asks you for either NS records or a CNAME record, and the two are not interchangeable. An NS record delegates DNS for the subdomain; a CNAME points one name at another. Both save cleanly at every provider, both look right afterwards, and only the one you were asked for works. Check which type you were given before checking anything else.
Only one nameserver was added
Section titled “Only one nameserver was added”This applies to NS setups. You will have been given four values, and each needs its own record with the same name and type. A single record is the most frequent version of this, because the interface makes it look like one entry per subdomain.
The full domain was typed into the host field
Section titled “The full domain was typed into the host field”Most providers append the domain to whatever you enter, so typing s2s.yourdomain.com into the host field produces s2s.yourdomain.com.yourdomain.com. Enter only the label, s2s. Check what the saved record actually reads rather than what you typed.
The records are on the wrong domain
Section titled “The records are on the wrong domain”Easy to do on an account holding several domains, and easy to miss afterwards because the records look correct. Confirm which domain you were in.
The trailing dot was dropped
Section titled “The trailing dot was dropped”Some providers require the trailing dot on a nameserver value and treat its absence as a relative name. If the values you were given end in a dot, keep it.
The subdomain is hosted as a primary domain
Section titled “The subdomain is hosted as a primary domain”The subdomain has to sit under the main domain’s registry. Set up as a primary domain in its own right, it is rejected rather than delegated.
It has not taken effect yet
Section titled “It has not taken effect yet”DNS changes are cached, and the old answer can be served for as long as the previous record’s time to live. If the records were saved minutes ago, waiting is a reasonable first step. GoDaddy puts the outside figure for a CNAME change at 48 hours.
Confirming it
Section titled “Confirming it”Contact support once you are confident the records are right. Delegation is verified from our side, and you will hear which record is missing or misspelled if one is.
While the subdomain is not resolving
Section titled “While the subdomain is not resolving”Events are not being collected first-party, which shows up as a low match quality score rather than as an outage. If you are chasing a poor score on a new web integration, confirm the subdomain first.