GMC Troubleshooting Guide
How to Fix Google Merchant Center Error: Insecure HTTP Image Link
Google requires product images to be served over HTTPS. HTTP image URLs are rejected and will keep items from serving.
FeedScrub flags any image_link that still uses http:// so you can update CDN or storage URLs to HTTPS before re-submitting the feed.
Paste your feed below to instantly isolate items failing due to this exact error code.