Problem exporting transparent png file.

I have an image with a transparent background.  I'd like to export it retaining the transparent background.  However, the exported png always saves with a white background.

Things I've tried:

in export as, file is set to png and transparent is ticked

I've tried saving the image as a png, and it saves with a white background

I've gone into my artboard tool and set the background to transparent

I've right clicked on the layer and tried export as png from there

None of these have worked for me.  So I'm thinking it might be a bug?  I'm running version 24.0.1 on windows 11.

Any help will be much appreciated.