Error message, how fix this?

i have an error message ; it says: “_Social Club account specified (my user name) does not own a valid license to GTA 5”. How i can fix this?

Buy GTA V ?

  

but i thought this can work on cracked version too if not then why dose fivem exist

No, you have to have a legit copy. This is so FiveM can stay up and avoid legal actions. “Why dose fivem exist” because some people like making their own custom servers.