"Failed to log in: Invalid Session", Launcher won't connect to the internet

My game launcher won't connect to the internet even though my connection is good. Whenever I try to refresh to connect to the internet in the launcher, it doesn't connect and it says "play offline" and when I do that and try to join a server, it says "Failed to log in: Invalid Session (Try restarting your and your launcher". I try to restart both but my launcher still wont connect to the internet.