useing thrusters at the gate

hello to all:
ok, I'm at karachi pakistan gate got the passengers loaded and leaving the gate turned on thursters and nothing happens and (yes the parking brake is off). it happens to alot on all my 380 planes is there a way to turn on thursters at the gate "yes" to get the plane to back up. all my other planes the 330's,350's,340's,777's,787's are fine with working thursters at the gate.
bombardier
ok, I'm at karachi pakistan gate got the passengers loaded and leaving the gate turned on thursters and nothing happens and (yes the parking brake is off). it happens to alot on all my 380 planes is there a way to turn on thursters at the gate "yes" to get the plane to back up. all my other planes the 330's,350's,340's,777's,787's are fine with working thursters at the gate.
bombardier