This post explains one cause of firmware updates/recoveries failing for the Line 6 POD Go. Hope this can help someone.
TLDR: prior to updating firmware, shutdown any and all applications that could conceivably use audio.
I rented a POD GO a couple of days ago, and the firmware was still at 1.40.1, so soon as I connected to POD GO Edit, it prompted me to update it to 2.0. Unfortunately the firmware update failed. POD Go Edit said it "updated successfully", but the screen on the POD GO device itself just continued to say "Updating..". I'm a software developer, and I know interrupting a firmware update is a big no no, so I went away and came back 30 minutes later. It was still stuck on "Updating..". At this point I sighed, turned the unit off and on, and it wouldn't boot past the "LINE 6 POD GO" screen (still shows firmware at 1.40.1). I tried a factory reset, but it doesn't get past the "Will reset Globals, Presets, IRs..." screen
The steps I took were as follows:
installed Lined 6 Updater
It doesn't see the device. Also tried another USB Cable and alternate USB port.
Tried booting POD GO holding "Page >" button.
Line 6 Update now sees the device, but the firmware update fails. Will try a different computer later.
Tried a different computer.
No luck. (this is actually very interesting, which will become apparent later)
The solution: Actually read the instructions presented in the Line 6 Updater (I know, I know, RTFM!).
The first instruction provided by the Line 6 Updater is:
"Shut down any programs that use audio or connect to your POD Go device, like DAWs, iTunes, Spotify, video games, etc."
So I opened task manager, and saw that Spotify.exe was actually running in the background, so I killed that. I also killed MS Teams and WhatsApp Desktop.
Tried the Updater again, and it worked!
The reason I mentioned earlier that it was interesting the update failed on the other laptop, is that it didn't have any of those applications installed. It did however have Discord installed. I suspect that was the culprit.