How do I make an arrow use a gradient color?

[AnotherMe]

I'm working with Adobe Illustrator CC 2018. How do I make the Arrow pen use the gradient color? I selected the gradient color in the stroke but it's not showing the gradient.

Thanks

[Monika Gause]

Can you plese show a screenshot of the problem that includes the appearance panel. Object must be selected.

[AnotherMe]

[Monika Gause · Accepted solution]

Seems like you have applied a brush.

You can't apply a gradient to a brush.

You will need to expand it: Object > Expand appearance

Then you can apply a gradient.