It takes time for all of the zone name servers located all over the world to update their lists. So, when you change your name server options in your Dynadot account, these changes must be updated to all zone name servers before your domain displays the correct web page. This is what people mean by waiting for their domain to resolve, since the zone name servers will, at first, contain your old name server settings until they update. Depending on the central registry (Verisign, etc.), they may update within five minutes or (very rarely) take a whole day to update.

Use the IP lookup tool in your Dynadot account to determine if your name server settings have been propagated.