@MasterSlycer Hello,
Do you remember when was the last time you played?
If you haven't played for a long time, there was a server merge back in 2017, which could be the reason why you need to rename your characters.
https://www.swtor.com/info/news/news-article/20171002#faq"It is our intent that this process will have very little impact on you or your account. Since Character names must be unique on a server, it is possible that when we create the new United Forces servers, you may need to rename your character. As part of the process of uniting the galaxy, we will communicate a specific set of rules to govern the prospective scenario where two names collide:
Premium players (Subscribers) will have priority over Free-to-Play and Preferred Status players.
Highly played characters will have priority over characters with less play time.
To limit the challenge of duplicated names we will proactively remove names from characters that have not been played within the past 90-days or more and which are below Level 10. We know your character'sname is very important to you and so we are taking steps to ensure that you can hang on to the names you love to the greatest extent possible!"