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The mechanical limit switches for the top and bottom floors are safeties only. They are there only to keep the elevator from overrunning the bottom floor into the pit (if there is one) or overrunning the top floor into the mechanicals and motor.

The actual floor stops are controlled by the magnet plates bolted to the left rail.

I would expect a code to be present on the hall stations when the elevator is at the top floor and won't work. That's the safety. Then, as you move the cab down just enough to un-trip the safety, the code should go away and the hall stations will act normally. I assume you are moving the cab down just an inch or so with the wheel on the motor shaft or with a pendant.

It sounds like there is a problem with the magnet plate, the magnets, the magnet hall-effect sensors or the circuit board that has the hall-effect sensors.

Things that come to mind that fit the symptoms you are seeing:

(1) The plate with the magnets is loose or was loose and is no longer properly positioned on the rail relative to where the cab lines up for the top floor.

(2) One or more magnets on the plate are dislodged.

NOTE: the magnets are North and South specific, so you have to know which side, North or South, needs to face the COP wall

(3) The circuit board that has the magnet hall-effect sensors is dislodged somehow. This circuit board rides in a metal housing on the outside of the cab and needs to be 1/4" from the magnets when passing them. There are some adjustment bolts on top of the cab.

(4) The circuit board that has the magnet hall-effect sensors is somehow electrically damaged. This will be the worst case, but I doubt this will be the case based on normal operation once you bring the cab down slightly on second floor.

(5) The magnet hall-effect sensor integrated circuit for the second floor (top floor) is dead on the circuit board and needs to be replaced. This was the case for my elevator and I scavenged the "third floor" hall-effect sensor and used it for the dead sensor. It is not actually the "third floor" sensor as the floors are bit encoded, but with only two floors, there is one sensor that is essentially spare. The magnet hall-effect sensor integrated circuit is just a 4-pin IC that is not hard to repair if necessary.

If you are lucky, a magnet on the second floor plate has come loose and it just needs to be re-positioned. There is a bulletin for this and it has you actually gluing the magnet down with epoxy so it doesn't happen again.