I have updated to the latest Domain mapping plugin and seem

I have updated to the latest Domain mapping plugin and seem to be having an issue now. I have tried to add a domain but receive the following error.

Domain name is unavailable to access.
We can't access the new domain. If you've just purchased it, please, wait while it will be propagated. If it is already propagated, please, check your DNS records to be sure that the domain is configured correctly.

The domain is several years old and I added the new A records several hours ago. Normally this works straight away, is there any reason this would not be working?