Thanks, guys - your input is appreciated. I contacted MTH Support about this issue and found the answer to the problem I had. It's root cause is in the expansion of my railroad empire! It turns out that, not only is the DCS Explorer limited to controlling 3 locomotives at one time, you can only have three locomotives configured in the unit at one time! I had three in there when I went to run the PS2 locomotive. The "fix" was to remove on locomotive that was not in use, then I was able to add in the old PS2 loco and everything worked fine. The problem is that, at least in the literature I've seen on the DCS Explorer that isn't clearly called out. (at least not clearly enough for my old brain to pick up on it!) The message that shows up in the app doesn't give a clue to this either, it just tells you to upgrade (translation: spend more money with us).
In the end, it's now working as it should.
