Connection Error

I was working on a project with a friend and we encountered a problem with one of our servers on the network. Sometimes when a player tries to connect once or twice they go on without problems and sometimes they are shown this error message:

Could not connect to a default or a fallback server, please try again later: io.netty.channel.ConnectTimeoutException

I have made sure that all of our IPs are correct, we are using the latest BungeeCord...

Connection Error