Why aren’t my product images showing?
WooCommerce POS uses the same thumbnail sizes as WooCommerce, you may need to regenerate your thumbnails.
WooCommerce POS uses the same thumbnail sizes as WooCommerce, these can found in WP Admin > WooCommerce > Settings > Products.
Thumbnails are created when you upload the product image to WordPress. If you have changed the thumbnail size after uploading the product image you may need to regenerate your thumbnails.
Thumbnail Settings in WooCommerce