I bought the registered version and it registers fine at the provided dialog window.
In fact, seems to even run fine... but then there is this repeating beeping, like a nag, every couple secs, and I get a dialog that pops up and says the license is invalid.
I think it's either FSUIPC, a Flight-Sim conversion to FSX-SE glitch, perhaps steam - but I'd suspect this is one area they would have handled decently; perhaps a pay plane but this just happens with any heli, stock or otherwise...but I am speculating surely.
So I have no idea what is going on - but your program might be it - might not - you'd know best :)
I have no idea if this is your program or not. I am not running to much. FSX, FSUIPC, HTR and the Oculus Rift DK2 (Virtual Reality) utility so I can fly in true 3d... which is free and doesn't require a license.