Registration code error

I have Synthesizer V Pro
I have never had any problems, but yesterday when I started the vst version in Studio One, I was asked to insert my registration code. I have no idea why it asked for the code. So I didn’t think much about it, and entered my code and everything works fine.
But after that, I realised that I now have used my code twice on this computer - for no reason. So I only have one registration left. If it happens again I end up using up all my codes?
On other software the registration codes are linked to a certain computer, that would be nice.