Can't align gradient across inside stroke

[default8vag7ibdibvx]

Hi.

I made this shape that I want to simulate a shadow in, and I've decided that I wanted to create an inside stroke to which I would apply a gradient that gets darker the closer to the border it is. But, for some reason, whenever I click 'align gradient across stroke' nothing happens.

Any idea how to fix it? Or how to simulate a shadow any other way? Thanks.

[Monika Gause]

Try and use the offset path effect instead of align stroke inside.