@Webpirat
You need to reset the password on the linked EA account that account has the persona webpiratsix (not Webpirat) that EA account uses the same email that is on your swtor account
use the following link to reset the password https://signin.ea.com/p/web2/resetPassword (put the swtor email in the link) then login on that EA account to fix the swtor account for purchasing
for future purchases, use incognito mode on chrome initially if you purchase on swtor.com to be sure browser cache and cookies is cleared