Banned yourself In your own server?

[Fiedlers2020]

If you were banned in your own server, first if you were banned by an admin, hacker etc. type /pardon (your user) in the console and you will be unbanned!

if you have some sort of hardcore server and died but need to come back then press spectate world and in the console type /gamemode survival (your user)

[DuckyProgrammer]

Actually, don't add the / if you're running the command from the console. The console automatically adds its own /.