The flaps in the Hawk are controlled by the standard flaps control assignments within the simulator. The most likely cause of the flaps remaining in the down position will be a control on your external hardware extending them. An easy way to test this is to unplug any external hardware (joystick, throttle quadrant, etc) and then restart a flight. If that fixes the issues, then that confirms the issue will be linked to the external hardware.
If the flap standby lowering system is triggered, the flaps will be locked in the fully extended position and will require a restart of the flight to reset.
Finally, if state saving is enabled on the EFB, the aircraft will load in the state it was previously left in. So if flaps were fully extended at the end of the previous flight, they will be fully extended at the start of the next flight.
Hope that helps.
Mark - Just Flight