It makes coloring lineart so much easier, but I can't find it on PSS.

Currently my only method for paying is my mastercard, but it seems the website just can't process it at the moment. I'd like to know if this is just bad luck on my part or if the issue's been around for a while.

I'm thinking of getting myself a key, but I'm a bit reluctant. Is the key bound to a computer or an user account of sorts? If I end up formatting my computer, do I lose the key and can't use it anymore? Any info in that regard is appreciated. Thanks in advance!