TriggerClientEvent not working

Hello FiveM.

I have been struggling with a problem for DAYS now. I cant get a client event to get triggered. It doesnt seem to do anything. Here is my server code. I use vRP but dont think this is the problem because it actually does print that he has the group.

local Proxy = module("vrp", "lib/Proxy")

vRP = Proxy.getInterface("vRP")

-- SERVER EVENT: CHECK IF POLICE
RegisterServerEvent('checkIfPolice')
AddEventHandler('checkIfPolice', function()
	local user_id = vRP.getUserId({source})
	local isPolice = vRP.hasGroup({user_id, "police"})
	if isPolice then
		TriggerClientEvent("playerIsPoliceEvent", source)
	end
end)

Local source = source After the handler