@MikeBrand456 Ok. So if you had the same problem as me then steam should say that your game is up to date and the problem isn't updating the game. What I did was go through my directory (since I had previously modded) and took out everything that seemed like it didn't belong (ASI files, INI files, Config files, LSPDFR files, ect.).
After this I went into my steam library and selected GTA V. I right clicked on it and went into my settings and then clicked on the Local Files or Local Data tab. Under this tab I pressed "Verify Game Cache". Let that Verify for a few minutes, after which steam notified me that several files were missing. I pressed ok and steam downloaded the missing files into my directory.
After this I started up FiveReborn and selected a server. After that everything works fine! Hope this helps!!