Hi,
From what I can see on your pages, it seems that HikaShop thinks that there are several images linked to this product. However, the main (first) image is invalid or doesn't exist anymore for some reason, and HikaShop is not able to process it. This is why the image doesn't appear with the tag.
On the product page, HikaShop displays two areas for the images:
- the main area, which displays the main image in a bigger size
- the thumbnails area, which displays a smaller image of each image linked to the product
That second area only appears when there are several images linked to the product.
And the small image you see on the product page of that product is in that second area. So that means that it must be the second image linked to the product, and that the first image can't be processed, and that's why it doesn't appear in the main area, nor in the thumbnails area.
So, I would recommend checking the images of that product. Delete them all, save the product once, and add back the one with works. It should hopefully be enough. Otherwise, you can always unpublish this product, create a new one with the same information and the image, and change the id in your tag so that it uses the new product. That will circumvent the problem.