I am a complete novice and accidentally deactivated my domain. I now can't see how to re-activate it. Any ideas? Please??
Do you remember what you did when you "deactivated" it? There are many ways that you could do something which would result in your domain being "deactivated". You will need to provide more information before anyone can really help you.
If it is urgent to bring your domain back online, contact DH support via DH panel --> Support --> Contact Support