Hi compguru,
can you provide some additional information?
1. What OS are you using
2. What ProRender build do you have installed?
Also you can try the following steps, as it may help fix the problem
Steps
1. Close 3ds Max
2. Open the Task Manager and make sure that 3ds Max is closed
3. Uninstall the plugin and re-install it
4. Open 3ds Max and check if your GPU shows in the render settings