Gallery Options Not Working > They're blank!

Issue: I have downloaded the nextgen gallery plug in, I understand how it should work and it should be all ready to go.

The initial screen to Add Gallery / Images to then add to a gallery is not working. You can select it, wait as long as you need but it’s blank. I’ve tried deactivating then re-activating and also un-installing and reinstalling the plug in but the same seems to occur. In fact, all pages are the same other than manager galleries which seems to work.

Can you please advise the fix? I am really interested in this gallery and I really need to add one to my pages very soon.

https://wordpress.org/plugins/nextgen-gallery/