I can't select the optical flow option on a clip.

I saw a video on how to correct your optical flow analysis speed, and it told me to delete my optical flow files (in my analysis files folder) and then to go back to FCPX and select optical flow on the clip you want so that the system will trigger the use of optical flow and will correct it. I tried that except that after deleting all my optical flow files, I couldn't select the optical flow option anymore on a clip.

I moved all of the clips out of the trash and tried again, but it still didn't work. I am not sure but I think the problem is that the optical flow files are not in the correct folder...

If anyone could help, it would be gladly appreciated .. Thanks !!