Yep, this has happened to me countless times now (bike bought April of 2015). Basically, I am at the point where every time I go to use my ST2, I'm afraid it won't work. Either the battery won't have charged, or the torque sensor will crap out, or the "Drive Error" code will show up, or the friggin' entire pedal assembly will literally just fall off the bike (yep, this actually happened). Today, I had both the charge issue AND the "Drive Error" message. To add insult to injury, I did the battery pop-out fix, and now my key is stuck in "unlocked" position on the bike. I can't jiggle it or anything, so I'm pretty much fed up with the entire piece of equipment. I've already had it in the shop 3 times, and it's still basically a piece of garage. It's a shame, because it's a pleasure when it works. But it fails to work so frequently that it cannot be trusted as a reliable form of communication. If I bought a car or a motorcycle, brand new, that would just randomly not start or would fail to "turn on", or if the accelerator pedal just fell off while I was driving, you better believe the manufacturer would be dealing with my state's lemon law. As it stands, I'm out $8000 and will never buy, nor recommend, another Stromer product ever again.
My suggestion: if this bike is still relatively new, try to exchange it for one from a better manufacturer. Your problems have only just begun.