Watermark doesn’t apply to thumbnails

Good day!

We have a collection of images on the gallery page. We are having issues with adding a watermark to the thumbnails, it seems not applying. But when you click on the thumbnail to view the full image, you can see the watermark. I have it enabled on the watermark settings so I am not sure why it is not applying on the thumbnails.

Kindly advise, thank you!

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