This is for everyone who has had this problem….. I had this problem. For about 4 months I was confused as !&&*. One day I decided I would bite the bullet and take a look inside. All that had happened is the flex connector had come loose inside the device, probably when I pulled out the usb. I clicked it back in place it worked. Take a look at this link at how to access it. Teenage Engineering OP-1 バッテリーの交換 Teenage engineering customer support is dead they never helped me. Hopefully this will help someone in the future :)