Users have reported that when trying to add or change a credit card, several EU countries are no longer listed as valid choices for the country of origin, preventing players from using these cards. Since there are no account transfers for SOE players to migrate to ProSiebenSat.1 accounts, this could mean locking players out of years of work on characters. SOE has made no official response regarding this issue, but it runs directly counter to what has been stated in the past regarding access and account ownership. We've contacted SOE for a response and will update with any further information.
[Update: Dexella on the SOE forums has posted that the studio is "looking into the EU/credit card issue now." Thanks to Erissei and Zjeven for the tips!]