TSX-Plus help needed!

OK, I have figured out how to modify TSGEN.MAC, use PUTR to make a disk image, load it in SIMH, reassemble, relink, and *finally* send it to an RL02 pack via vtserver! TIme-consuming but doable. I've been wrestling with this all day. BUT - TSX+ 6.50 just will not run. At all. Using RT-11SJ (5.01), after typing "R TSX" I can hear the disc access for a few seconds, a pause, a few more accesses... then nothing. It just hangs. Nothing on the console either., no response to <CR>. When starting it in SIMH (the same disk image), I get the error message ?TSX-F-Computer line clock is not working. Figured that was just a SIMH thing. But the address/vector is correct in TSGEN.MAC... and when checking TIME in RT-11, the seconds advance in real-time like it should. On the real hardware, the error message doesn't display, and the clock is running... My old version of TSX+ is 6.16 and it runs fine on console and SLU 2, just needs rebuilt to use different serial cards than the original system. So where should I start looking first? RT-11 version incompatibility? Any TSX+ experts online? Thanks for any help. This is driving me nuts!