Same here, I started with msfs around christmas, manual cache never worked. Mostly the whole option is greyed out, sometimes I can access it but all options on the satellite map background are greyed out.
If I copy and rename the rolling cache .ccc file it is possible to start a download of an area but I cannot change the size of the cache and downloading causes a crash. So that’s no workaround.
Since my internet connection is fairly slow I really would need the manual cache! If anyone has a solution, please post it:-)