When I tried to install the HL7 Accelerator for Microsoft BizTalk, I received the following warning message:

Error: Installation cannot be performed because the BizTalk server has not been configured or user account is not a member of the BizTalk Server Administrators group.

I was sure BizTalk was configured and my domain account was member of the Biztalk Server Administrators group.

Eventually it did turn out to be a group membership error.
Apparently  the HL7 accelerator isn’t designed to be used with domain local groups. BizTalk Server Administrators and BizTalk Operators must be a Global Group, as stated here.

So I started experimenting. It appears that it can be a universal group, but when I add a user from a different domain to that universal group, I can’t install HL7 with that user account it fails. But with a user from the same domain it is no problem.