Friend can't join me

[blade4]

So I started a server weeks ago and everything has been good but ever since I added simple mods, It started off good, then later when we got off for a break, then got back on that message appeared and we have tried for days fixing it to no avail. We tried unsubscribing from the mods and playing without mods, deleted and redownloaded the game, deleted the vehicle file then redownloaded it, we have done everything, if there's a fix to this, even if we have to reset I don't mind cause the same message appears when I try and join him.

[Beard]

Follow the path as shown in the screenshot to your game folder / media folder.
Delete the "scripts" folder in that path.
Then verify your game files:
Steam Library > Right-click Project Zomboid > Properties > Local Files > Verify Local Files

Have your friend do the same thing, then it should work fine.