Just had this happen to me. Forcing a re-install and re-download when using F4SE launcher. As yet I have not isolated what causes this. 1. Launch game with F4SE. 2. Normal Game Launcher gets activated instead of loading into the games main menu. 3. This continues in a loop and I'm unable to start the game through F4SE. I'm re-installing now.. will update this later if I find a solution. One possible issue, I'm thinking my problem was launching the game in online mode after I had cleaned some of the main game files, which got detected forcing a re-download of all the game files. I'll need to make sure I'm only in offline mode next time, though I'm not sure why F4SE launched the games launcher...