You can only ad in the lobbys, and if you want to tell your players ad messages, dont do it in the lobbies or someone elses server, only in yours. If you do it in other servers you will get muted for server advertising and self promoting
Hello. What was the name of the world called? I recommend naming it one word like
Spawn
SmpWorld
Smp1
World names must be 1 word. Make sure your world name is has only letters or numbers. Any other characters will confuse your file manager.