Possible fixes GTA V not starting include

1. Your computer might have marked steam_api64.dll file as a virus. try excluding file from antivirus/defender or try turning antivirus off or you might try downloading from popular dll files sites online and replacing original file

2. Also GTA V could get stuck on a black screen for a number of different reasons. It could be because of conflicting software running in the background, corrupted game files, or out-of-date graphics drivers. You can try updating your graphics drivers, updating game, checking the game files through the game launcher, and making sure that no other software is running that would be incompatible with the game while you are playing it. Contact the game's support team for additional assistance if the problem persists.