Jumper T8sg V2 seems to have lost software install

My Jumper T8SG V2 seems to have lost it's software installation and screen just shows USB symbol when radio is turned on. Radio will not respond to any inputs from buttons.I have downloaded new software but can't figure out how to get it to install in transmitter. Not sure if transmitter has an internal failure. Just would not show anything but USB symbol when powered on. Any help would be appreciated. Pete
Update:
I believe I have a problem with the electronics. Have tried everything I know. Can anyone help me find a repair facility for Jumper products. This is my second Jumper TX. My first one was DOA. It was lost trying to return it to Banggood (probably stolen in Chinese postal system according to Banggood. Purchased my second one (T8SG V2) on Amazon and had it working okay.and I was just learning the software. Turned it off one evening and when I turned it on the next day I encountered the symptoms in the original post. Any help would be appreciated.