Hi there,
"Finish button not clickable" is a bug of page.
To solve this problem you must use the English version of the registration page.
In right-upper corner select Settings->Language and pick English. It will redirect you back to the page and after you tick the "accept terms" checkbox that "FINISH" button will activate.
They are fixing this bug in the next days. Anyway now you know why that button was so wierd.
NOTE: there's also a second bug where some credit cards are evaluated as "prepaid cards" so it will keep giving you error "prepaid cards are not accepted".
Kind Regards