'The game's integrity couldn't be verified' error

[Sergentium]

I was playing this game for 2 years and everything worked normal. Suddenly when i run it it says it and i have done these things:
1.Reinstall the game 5 times.
2.Tried some of the things as -unitywebrequest, etc.
3.Read some of the other reports with same problem.
4.Checked the files from steam settings.
5.Tried to verify files from steam settings.
but its not working and doing the same thing: it runs for 5-15 secs on the loading menu and then just close itself and shows that error...

[Akihiko]

same

[DI_INQUISITIVE]

You need to go to your local files and find the "mono.msi" file.
then click on it and the installation will begin. After installation, you will be able to enter the game

[AErthur]

^reply 2 is ♥♥♥♥♥♥♥♥, doesnt help

[Reshiram-Solis]

locked due to necro.