try this take battery out for 10 seconds reinsert while holding down both volume rockers and insert usb install qualcomm port driver on QHSUSB__BULK (if windows 8 8.1 and 10 enable test mode first)_ from hereand use qualcomm flashing utility from the folder to flash a fresh firmware for your jolla c(sorry i own a intex aqua fish and they arent exactly same to be cross compatible with firmware so you need to find firmware on your own) [P.S. the folder isnt actually been made complete as im uploading stuff constantly wait for a little bit for the qualcomm tools to be uploaded must be done by the time you read this ] also refer to this tuitorial for exact steps for qualcomm flashing on sailfish devices(btw theres a slight chance that the imei would be gone so you'd have to rewrite it ive included a tool that allows imei rewriting after flash just in case you have a corrupted imei)