The “error” is completely normal, and should not prevent you from accessing PHP. Our FTP servers kick you out if you don’t do anything for 20 seconds. But if you login, navigate to the folder and start your file transfer, this timeout should not cause any notable issues.
That said, there are cases where the server kicks you out before you’re fully connected, which usually has to do with messages being lost along the way. But to figure out what exactly happened, can you please share the full connection log, rather than just the last message?