If you do not have an NVIDIA GPU with CUDA then you cannot use GPU acceleration for Ray-traced rendering. If you have installed the Cuda drivers and you cannot select the enable unsupported GPU box and you must uninstall the CUDA drivers. GPU acceleration only helps with Ray-traced rendering turned on and that feature is no longer being developed or supported because of changes that NVIDIA made in their product line. The latest versions of AE now come with C4D lite and Cuneiform which replaces all of the functionality of Ray-traced rendering, is supported by a lot more GPU's and gives you more options by a factor of about a thousand. Nobody I know that uses AE professionally uses Ray-traced rendering because it's so limited, a terrible waste of time, and anything that can be done in that rendering mode can be done better and faster using other tools. Everything except a very few 3rd party effects and the C4D rendering engine in AE is all CPU driven so enabling GPU rendering will not give you any advantages at all for any AE work except when you use the Ray-traced rendering option.
There are hundreds of threads on this subject. There is no fix if you don't have a very narrow range of GPU's that were supported by AE and NVIDIA so I wouldn't worry about it. Just check the never show this warning again box that pops up when you set the Comp rendering mode to Ray-traced rendering and don't worry about it.
That box is really only beneficial for the ray-traced renderer. That feature is considered obsolete. So, if I were you, I wouldn't worry about it. There are much better ways to do 3d in AE. Third-party fast-rendering options like Zaxwerks 3d Invigorator, Element 3d, etc. are great. But, if you don't want to cough up money for extra plugins, you have the HUGELY powerful Cinema 4D for free with AE. Granted, it's a Lite version, but you can do a lot with it! Tutorials here: Cinema 4D Lite Reference [Video Tutorial Playlist]
The only way you will get that box to be clickable is if you have an NVIDIA GPU that matches certain specs. Since you have an AMD card, don't install CUDA or anything! That will cause problems! See this: Avoid installing NVIDIA CUDA drivers on computers with AMD GPUs