According to the database, you have been banned by Sentinel, the anti-cheat. If you think you were falsely banned, please follow this steps:
First, try appealing here:
https://appeals.cubecraft.net you can appeal here declaring that you were not using a client and you think you were falsely banned.
If your appeal gets denied and you still believe that your punishment was false, then please contact the creator of the anti-cheat CrazymanJr. Please contact him on Discord. (@CrazymanJR#4742)
Make sure to not spam him since he's really busy. He'll take a look at the logs and he'll try to solve your problem as soon as possible.
If you admit you were using a hacked client, then please write an appeal right here:
https://appeals.cubecraft.net
You can appeal with the code that is showing on the ban screen, make sure to not share the code.
State why you used a client and explain why you deserve and should get unbanned.