"Unable to connect to the server" glitch

This issue is happening to me on PBE, I don't know how to fix it. The launcher works fine, my internet is fine, but when I try to load into a game the screen turns black and the message "Unable to connect to the server, Please check your network connection and attempt to reconnect to your game" pops up. I have tried restarting my computer, task managering league shut and restarting and restarting my internet, but none of this worked. When the game ended it allowed me to honor a teammate. If anybody knows how to fix this, please tell me.