CANNOT SIGN IN/SYNC

CANNOT SIGN IN/SYNC

I'm on a Macbook Pro but for some reason, my acc got signed out from my Notebook app, and couldn't get even to the login page no matter how many times I try. Works fine on Chrome, but it's such a hassle that it wouldn't sign in on the app...

It would just flash, and then turn into a white blank screen....how do I fix this???