After trying a bunch of things it seems to be working again. I'm not sure what fixed it or if it is fixed permanently, time will tell. Here is what I did:
- Uninstalled picoscope with "sudo apt remove picoscope"
- Uninstalled dependencies with "sudo apt autoremove"
- Installed older version of Picoscope by downloading individual packages (libpicoipp, libpl1000, libps2000, libps2000a, libps3000, libps3000a, libps4000, libps4000a, libps5000, libps5000a, libps6000, libusbdrdaq, and picoscope) from https://labs.picotech.com/debian/pool/main/
from around January 2015 and installing with "sudo dpkg -i *.deb"
- Marked picoscope to hold at older version: "sudo apt-mark hold picoscope"
- Installed older picoscope dependencies: "sudo apt -f install"
- Discovered that older picoscope would not detect my PicoScope 2205MSO hardware for some reason
- Uninstalled older picoscope: "sudo apt remove picoscope" and "sudo apt autoremove"
- Found that picoscope package configurations were still installed
- Performed a purge on all picoscope related packages: "sudo apt purge libpl1000 libps2000 libps2000a libps3000 libps3000a libps4000 libps4000a libps5000 libps5000a libps6000 libusbdrdaq picoscope"
- Reinstalled latest picoscope packages: "sudo apt install picoscope"
I suspect the purge operation may have actually been what fixed it, but I'm unable to confirm this. Perhaps someone else who is having this issue can try just the last 2 steps (purge and reinstall) and see if it fixes the issue for them.
In the process I also changed the USB cable to the original blue one that came with it. But I changed it back to the previous cable and it is also working fine, so I don't think that was it.
At any rate, I'm very happy that it is working again, since it was severely impacting my ability to troubleshoot. I'll be sure to post any updates if I have any more information. Keeping my fingers crossed that it continues to work..