no one is reeving my messages on servers.

When I go on servers and type in chat (Eg. Hello can anyone see this?) It never gets sent I dont get a reply and no one can see it. I know that because I tested on my other account. I thought it was only on one server but is dose this on all of them. It first I thought it was a shadow mute so i contacted Mojang support but they said that they don't mute players and sent me to here.