Minecraft Wont let me play online servers

When i open the launcher, and i try to play on an online server, it says "Try Restarting your game" This has happened to 5 of my friends so far, and we researched it and it said that mojang thinks we illegally downloaded the game, even though i bought it in 2013.

I expected to be able to play on my usual online servers.

It wouldn't allow me to play online servers which upsets me because ive spent a lot of money on them.

Steps to Reproduce:
1. Open minecraft
2. Click on Multiplayer
3. Try to join an online server (Mineplex) Or any server works.