I'm sorry, we - the forum team - won't know why you were banned.
Can you take a look through your emails? Usually there should be an email, Terms of Service aim to send one out when a ban has been added that shares the general rule broken for example: ban applied for cheating/hacking/hate speech/etc. This article shares more about Apex and the rules: "Play by the rules in Apex Legends".
＊Accept as Solution button- If a post answers your question please let us and other players know by hitting this button.
＊Me Too button - 'Me Too' helps us track how many players are also experiencing that issue. Definitely make use of this button.
＊XP button - Say Kudos and help players 'Level Up' by giving them XP for helpful posts.
Please only DM me if I've asked you too, or in the case of highly sensitive content. General questions/issues/topics are best shared on the forum where others can take part/benefit from the responses/solutions/workarounds