Legendary Weapons + Enhancement Scrolls don't work?

When I tried my 100% Adv Enh Scroll on my lvl110 Legendary gun, it said "You can't use scrolls on this item".

Does that mean you can only use Legendary Scrolls on those Legendary Weapons?

Normal Enh Scroll didn't work either...

Item wasn't scrolled yet (7 slots open), is it needed for Enh Scrolls for an item to be fully scrolled?

I didn't scroll for myself in like 3 years... so yeah, anyone explain plz!

yes the equipment needs to have 0slot before it can be enhanced