Right Click on the source and select INTERACT...
nope, screen is right size, it's the fact that the pop-up doesn't actually pop up, i've been searching these forums for a solution and a few other users had the same issue but no solution was found till date!If you resized the browser source when you added it the sign in my bee off screen
Try making the browser source full screen and see if the sign in popup is visible then.
That also may happen if you crop the source to show only what you need...