Well, welcome to the pain of LSPDFR.
I'll give you a short catch up. Rockstar hates modding, and for modding to work properly you need Script Hook 5, which is giving you the error here.
Since Rockstar despises modding and sees it as the literal work of the devil, they constantly make unnecessary updates in order to screw with the modding community, creating a
need for the mods to be updated. In this case, it's Script Hook 5.
This isn't a problem when SHV is updated, but when we have to wait 5 days for it to upgrade? That's a problem. Otherwise, it's a great thing, load of fun and you'll enjoy it with the correct
modifications and plugins.
Final answer: This is a problem that will be fixed soon, and happens every few weeks. Script Hook 5 will be updated soon and you can actually start the game.