Why won't new widgets show on the "add widget" screen?

[AC Question]

Hi!

I recently purchased a new LG G4 device, and encountered a problem: when I download new widgets/apps that include widgets, the new widget doesn't appear on the "add widget" screen. Widgets that arrived with the OS are there, though.

(Obviously, by "add widget screen" I am referring to: long press on sceen => edit => widget)

What am I doing wrong? What can I do about this?

Thanks!