After full formatting the GPU still doesnt work then it might be dead. It has happened multiple times that after updating drivers AMD GPUs just die. Might be a coincidence but i have seen some post where victims faced the same issue.
Also sometimes manufacturers give GPU BIOS updates too ( So look for yours it might get it back to life )
BIOS Update – gpuShack
Before proceeding keep in mind that Bios update is a very very risky process and you must use only the bios made for your own hardware.