I am just before implementing screen space ambient occlusion in my game, but first I wanted to try enabling it from NVidia control panel only to find out that it is greyed out so that I can not enable it. With this I could enable SSAO for some other games, but not every one. I know this technique requires the depth buffer and (optionally) a normal map texture to sample information from which I already have access to given I have a deferred renderer working.
After that I actually thought to roll back to a previous version of my game which still uses forward rendering so the depth buffer is actually bound to the backbuffer which I render to from the get-go so that maybe the NVidia control panel would somehow make use of it. It was not working with forward rendering either. (I also tried FXAA in the control panel and that works - but it doesn't need any depth or normal texture)

So my question is that how can I enable this function so that it would work by enabling it in the NVidia control panel?