Did a quick google, try this.
"1 First, go where you have installed the gtav.exe my is in D:\Programmi\GTAVLauncher.exe
2 Now create a shortcut of gtavlauncher.exe, right click and hit proprieties, now you have to add -verify after your directory here an example
D:\Programmi\GTAVLauncher.exe -verify
apply and save
3 Done, hit the shortcut and the verify will start!
Hope this helps !"
Try this and see how it goes.
Source: https://support.rockstargames.com/hc/communities/public/questions/203855567-Here-how-to-verify-gtav-files-from-Social-Club-launcher-PC