Can't buy subscription

Hi,

just wanted to come back to the game after a while, my old account and characters are still here. Downloaded the game, now wanted to buy - and cant. Used to pay by PayPal, now added a Mastercard card and at the last step of the purchase I get: An error has occurred while trying to process your request. Please, try again later. {0}

Help please, what is wrong? I've read several threads here about linked EA accounts etc. - I do have one of those but was never linked to my SWTOR gaming. Still the threads mentioned other error messages, not sure if relevant for me.

Thanks in advance. P.