[Threshold]

As mentioned above by Pottus, this is your error.

This information is referenced on the SA-MP wiki.

Quote:

Originally Posted by SA-MP Wiki Players can not damage/kill players on the same team unless they use a knife to slit their throat. As of SA-MP 0.3x, players are also unable to damage vehicles driven by a player from the same team. This can be enabled with EnableVehicleFriendlyFire.

References:
https://sampwiki.blast.hk/wiki/EnableVehicleFriendlyFire
https://sampwiki.blast.hk/wiki/SetPlayerTeam