Try using Pinterest's Debug Tools
First, check with our free tool Social Share Preview which images are visible for Pinterest on your site. If you don't see the image you want to pin, there might be an issue with your site – maybe because of lazy loading, or the wrong image formats.
It could be that Pinterest did not check your site for a new image yet. Use the Pinterest Rich Pin Validator to tell them to do this. Just enter the URL and click "Validate".
Check your image implementation
Per default, Pinterest should pick up any images in your content as possible pins. If you want to make sure its finding the right (high-resolution) one, we recommend using the data-pin attributes on your image tags:
<img src="visible-image.png" alt="The image my users see" data-pin-media="full-size-pinterest-image.png" data-pin-description="Pinterest description and #hastags" data-pin-url="https://your-url.com" />
With the attribute data-pin-nopin="true", you could make sure an image can't be pinned - so check that it isn't accidentally set. There could also be issues with lazy loading or wrong image formats (for example with webp).
Placid for WordPress: Do you want your image to be visible on your posts or pages?
If you use Placid for WordPress, note that your Pinterest image will not be displayed in your blog article. Only Pinterest will be able to pick it up and show it to users that pin your article's URL.
If you want it to be visible in your blog article, this is the way to go:
Save the Pinterest image in your media library and add it to your article
Go to the article where you want your Pinterest image to show up. In the Placid-Settings below the article, change to the Pinterest tab. Click on the button Save to Media Library.
Place your cursor wherever you want your image to appear in the post text editor and add the image from the media library.