Can't get custom image size to work, even after regenerating thumbnails

Hi,
When I add an image to a foxycart product taxonomy, I get the overlay window and I can see all the image sizes including my custom one. But when I select my custom size I only end up with the default thumbnail size of 150 by 150.

I tried regenerating thumbnails and nothing is changing.
Am I missing step?

Thanks!

https://www.ads-software.com/extend/plugins/taxonomy-images/