This one just worked for me! I Already have about 40 mods installed, graphic things, cars , Gameplay Changers etc.
So i read in a forum that u cant mod Pirate Editions from GTA 5 so u have to verify it, because ur mod folder is stupid.
1: Search for ur GTA Folder. Mine is located in this path :" C:\Program Files\Rockstar Games\Grand Theft Auto V".
2: Search for ur :"PlayGTAV.exe" and create a shortcut.
3: Right click on ur Shortcut and click Properties.
4: Look for the Target Line (For me there stands this : "C:\Program Files\Rockstar Games\Grand Theft Auto V\GTA5.exe") and add an -verify behind it.
So it should look like this (For me) :--> "C:\Program Files\Rockstar Games\Grand Theft Auto V\PlayGTAV.exe" -verify <--
(Within the Arrows)
5: Save and close the Properties Window and start GTAV over your fresh created (-verify) Shortcut.
Your GTAV Launcher should Verify ur Files before it starts if u did anything right.
... Found this as i searched for Pictures