Too late with some info here....but FYI.. the KX-TD has to be a version 5,6, or 7 to communicate to the VM it's in Night mode / utilize "PBX Control" in VM.
Customer's is probably earlier version.....and the fact they had a TVS100 would point to that as I believe it was an earlier version of the TVS series. (Side note: Can't handle the slowwww speaking Digital Debbie on those H.D. versions)