Custom Backgrounds not adjusting to screen size

Hello!

I recently installed this plug-in and it’s working great, except I don’t see a difference in the background scaling when I choose ‘Cover’ versus ‘Flex’. I use dual monitors, one of which is a 15″ laptop. The other is a 23″ LCD screen.

On the 15″, the registration link on the bottom falls into the bottom border of the background, which is fine. On the larger monitor, however, the registration and forgot password links fall outside of the screen. I’m not sure why this is happening. I want the background to be dynamic enough to adjust (keeping its ratios) depending on the end user’s screen size.

Any suggestions on this?

https://wordpress.org/plugins/custom-login/