I am trying to add a stroke to an imported image, but the stroke never shows. Help why it not work?

I figured it out I did effect > path > outline object and now the stroke shows

It doesn't need to be embedded. Use a Convert to shape effect on the stroke

You may try to add a stroke in the Appearance panel. 

The image must be embedded and the stroke needs to have an Outline Object Effect applied.

You can make it an Object Style.

Pixel-based images placed or embedded into an Adobe Illustrator document can't have strokes added directly to them. Even tricks with the Appearance panel don't work. The solution is creating a box the same size as the pixel-based image, applying a stroke to that box and then aligning it to the image. Move the box behind the image if the line stroke needs to be set behind the image.