I think that jumper must be in the wrong position. It’s the only reason I can think of that it would be happy with 1 less port than is actually there. Not like your LON config changed or someone added an extra L24 card into the loop. I’ve seen those header jumpers just need to be re-seated too.
For the serial adapter, first look in device manager to see that your adapter is there and what port it’s been assigned. Then open IMS and set the com port to that. If you’re using the Triplite Keyspan adapter that we use you can open the Keyspan Serial Assistan to check that it’s connected and see what port it’s set to. I do recommend using the Keyspan adapter though, it’s the only one I’ve seen reliably work on every controller. I’ve had a couple with Prolific chipsets that worked fine on TAC20 and TAC32 but wouldn’t work on a TAC50.
