Not sure if this is the place, but here it is.
Today I was playing around with the presets and cycling through them using the physical button. I went to change the preset again, and it froze. It wouldn't change, and no sound came out anymore. It didn't matter if it was BT or the guitar input. I force it shut down, and then it didn't power back on.
Oddly enough, my phone was still connected to BT. Nothing was actually working tho. The app didn't see it as connected. Tried a factory reset and got nothing, no lights, no response, no nothing. I then plugged it into a wall outlet to see if it would charge. I thought maybe it was just completely dead. The charging indicator actually came on, which was surprising because it hadn't earlier.
This means it was actually off, not just frozen.
The Spark Go has to be turned off to be factory reset. I did the sequence on the Positive Grid website, and it actually worked. It turned back on, and I was able to connect it to the app and my phone with no problems. It now works just like it did before.
This whole process took me about an hour and a half because I couldn't find anything about this.
TLDR; try to factory reset, if no lights come on, plug it in to see if the charging indicator comes on. If it does, do the factory reset sequence again, and it should work, and turn on after.
Hopefully this helps!