Textures won't import, option disabled? Can't unpack Unity package textures.

Hi Everyone, Basically, I can't enable the tickbox to import textures for an asset from an Unity package, even though it shows it.

Attached is a screenshot of what it does. Basically the tick doesn't appear when I click the tick box. It goes grey to press down state, but no tick.

Anybody have any idea why? This is happening on my friends Unity as well. We can't send unity packages to each other, because it doesn't let us import the textures.