I do not see my GPU on the list of Devices on GamerHash App, why?

Most likely your GPU is not supported by GamerHash App. At this moment we are supporting Graphic Cards which have at least 2GB of VRAM (AMD) and 1GB (GTX) like:

-AMD Radeon with minimum 2GB of RAM: 7xxx, 2xx, 3xx ,4xx and newer

-NVIDIA GTX: all supporting technology CUDA 2.0+ with memory minumum 1GB