All RAR files I have downloaded from Rapidgator won't open - says "nothing to extract"

hatman, try a different archive program. There is more than one version of the RAR spec, and older archivers (or just crappy ones) won't handle newer variants of RAR. E.g., I find that The Archive Browser fails on a lot of them, while Unarchiver and WinZip and 7Zip will work with the same files without errors On a Mac, both UnRarX and MacPAR Deluxe seem to also work fine, though the first of those is getting kind of old and will probably have problems in a year or so, unless it gets updated.

If none of them work for you, then you have a corrupt file; try downloading it again, maybe through a different browser or with a VPN or whatever, to be 100% sure you are not dealing with a cached copy of the same bad file. If it STILL won't work, the file on the server side may be corrupt, but it sounds like this is happening to you a lot, which is an indication that the problem is on your end.