You have been banned by sentinel, It's cubecraft's anticheat. But, If you made an appeal and it's denied and your sure that it isn't a fair ban you can start a conversation with @CrazymanJR, but be patient your not the one who is banned by sentinel.
You can talk with CrazyManJR on discord too:
CrazymanJR#4742
(No need to spam it won't make any sense).
Goodluck.