Mixed Content when editing a page

Hello,

I had a problem with mixed content.

This plugin resolved the problem if I chose the capture option.

However, when viewing a page with images it does not report anything, so when editing the page reports a problem.

Mixed Content: The page at '<URL>' was loaded over HTTPS, but requested an insecure image '<URL>'. This content should also be served over HTTPS.

Only pages with images show the problem, others work correctly.

Why does this happen and how do I fix it?

Please give advice.

Thank you