This issue occurs when dynamic templates created within SendGrid do not render the thumbnail image when the template is created.
Troubleshooting
- Send a test email within SendGrid's template editor
- Look at the email and see if you can find any images not rendering correctly.
- If you find an image not rendering in the email, go into the template editor, delete the image component, then re-upload the image.
- Verify that the URLs for the images you're using in your template are correct and accessible. The URLs should be absolute paths starting with
http://orhttps://. - Ensure that the images are in a supported format (such as JPEG, PNG, GIF) and are not too large in file size. Sometimes large image sizes can cause timeouts or other issues.
- If your images are served from a domain that has firewall rules or is behind a content delivery network (CDN) with strict rules, it might restrict access to the image from SendGrid's servers.
Workaround
- Delete any inactive versions that do not show the thumbnail
- Recreate the template but do NOT clone the failed template.