Okay, just checked and yes, it is the “Gear Advisory” warning button that needs pressing… Not sure why it keeps ignoring it and repeating the warning though.
I’ve just tried taking off, got the warning once despite not raising my gear, flew a bit further and retracted the gear, and it stayed quiet up until I tried landing in a lake at which point the warning repeated again once I made contact with the water - but the only way I could get it to repeat was by coming in hot and bouncing across the lake, once I’d stopped skimming across the surface it went quiet once more.
I’m sorry I can’t help any further!