We can't know. You have not provided any system info or details about what you are actually doing.
If you want to use the Ray-traced rendering function in a Composition and you do not have a NVIDIA GPU with CUDA acceleration and you do not want to see the dialogue box again click the Never Again box in the warning and live with the very very slow rendering times. If you do not need to extrude or bend a layer then DO NOT use Ray-traced rendering in your project and AE will run faster and generally work much better all around.
If you are new then please learn the basics. If you want to use Ray-traced rendering features then read up on it.
I get back to you once I try my hard luck on it.