I know nothing about ext. 27. The point is it doesn't even ring. The other fax machine rings and answers, plugged into the same jack. The new Samsung obviously won't answer if it doesn't ring.

I get outgoing dialtone and can make calls from that machine. The moment the Samsung is plugged into a jack that's wired BEFORE the system, it rings like a charm.

There's nothing I can see in the programming of the fax machine that would make this happen or not. Obviously, ringers are turned on, etc.