So, the purchase button actually does have a function it takes you to your cart with the surname & coat of arms within it looking like this:

However, I'm guessing that if you already have that, it doesnt take you there as you already have purchased it?

That button uses Javascript and not HREF to complete the process.

If you have Javascript disabled, the button will not function.

Can confirm it all works for most - if not all other - people. If you are still having issues (it wasn't javascript being disabled) why not try jumping into the official discord? They have channels for assistance and bugs.

https://discord.gg/chroniclesofelyria