HELP, I can't join there is an error Mojang Authentication Servers are down! We can not let you join unless you are on the same computer as before... i don't know why pls help me..... .....FAST.... thanks
The mojang servers go down and come back every ~5min. Just keep trying to relog and you will be able to come on!
Mojang authentication is down, and you cannot join the server unless you're on the same IP / same login place as your last login.