Ring groups and SIP

Hi FreePBX’s

Hoping someone can help with some basic config info.

I have three SIP phones, on extensions 201, 212 and 213. I can dial each one for each other and they all work. But if I make a callgroup with any/all/one of the numbers and then try to call it, no extensions ring and the “Destination if no answer” rule is invoked

Any ideas what I might have set incorrectly?

Thanks