There is an issue with your Electronic Arts account - Can't Sub

@Gemmi88 

it will be Tuesday before a response due to holidays, alternatively you can call swtor support when the lines "are open" (Monday only English line is open due to holidays) and they can assist checking the account for issues

https://answers.ea.com/t5/General-Discussion-Technical/INFO-Getting-Help-and-Board-Guidlines/td-p/48...

generally the common issue is that the linked ea account has been disabled and or its data has been wiped usually due to inactivity 

no game time can be added , so if you try to buy on steam , steam will take your money but no gametime will appear on the swtor account , same for codes

if you know the email used to "create" the swtor account , use this link  insert that email address

For the steam purchase email uncropped screenshots using your email address on the swtor account per https://answers.ea.com/t5/General-Discussion-Technical/INFO-Steam-Purchase-Not-Working/td-p/9356718/jump-to/first-unread-message