Cannot connect to any Minecraft Server

When I try to connect to any server at all, like Hypixel, it says "Invalid session, try restarting your game and your launcher". I tried doing that many times, but I get the same results. Now, I have played the server many times and suddenly I can't go in! I tried uninstalling the game and reinstalling it 2 times but it still doesn't work. Please help. I don't know how to resolve, sorry.