Touchscreen AND Buttons Not Working

Nothing works on the quick start menu anymore. When I tried to resync it, only the + and A and B buttons work, but that only gets me to make a new Mii. I can't get to the normal menu to see if anything's working elsewhere. I've also tried unplugging everything and plugging it back in, but that failed too. I'm no longer under warranty, so Idk what to do anymore.

My Wii U is about 2.5 years old. The controller has no physical damage, and I keep it in a plastic bag on the stand to protect from dust and such.

I'm pretty much at my wit's end, trying to figure out what's wrong.