Mmm are u take any error in debug? if you did, show us to what is error. First, try to this:
Change this your code in server-side:
function GUIness(player)
local taccount = getPlayerAccount ( player )
if isAdminAccount(taccount) then
triggerClientEvent(player, "openGUI", player)
end
end
addCommandHandler("balloon", GUIness) --Command for opening GUI
and change this in client-side, too:
function openGUI()
if (cWindow ~= nil) then
guiSetVisible(cWindow, true)
showCursor(true)
end
end
If it'll not work, send error to here.