Did you refresh page with your images after watermarking? Sometimes WP shows old (cached) images. Try to force-refresh (CTRL+F5) site or download images (sizes selected in settings) and check them for your own.
Please tell us which image sizes you selected?
Is it ‘specific custom post’ type or ‘all’ images?
Can you provide link to watermark and image?
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After you register and login to the site, you may post all plugin support questions in the Support Forum.
If you need to provide private info, please create a ticket and then reply to it using Set as private reply option.