Minecraft Authentication

I'm on the 2017 MacBook Air and recently I can't play minecraft. It gives me the server authentication error and I know it's on my part because it works for everyone else. It's just this laptop that is not working as I have tried on my sisters (same model) and it worked perfectly, so it's nothing to do with minecraft or mojang. I've tried most things people have suggested, from the terminal logs to the IVP6. I tried the IVP6 and it worked once but afterwards I could not log in again. It's only online multiplayer servers I cannot play. Any help appreciated!