Is my right DI2 shifter bad? It will shift "up" but not "down"

The left shifter and front derailleur work fine. The right shifter works fine if I shift to a smaller gear; the bike does not respond if I shift to a bigger gear. I plugged into my PC and from there I could shift with the rear derailleur; so I assume that is not an issue. I have had the bike about a year and it never had an issue until now (so, not a connection loose from assembly anyway). I have not unplugged/replugged any of the connections yet as I understand I would need a special tool for that. I would guess that if the shifter connection were the problem, then the bike would not shift either up or down. Anyone seen this? I hope I don’t have to replace the shifter. (R8050 system, gravel road bike w hydraulic disc brakes)
Thanks