Blocked loading mixed active content / image

Hello there!

I searched the forum and found similar problems, but not 100% mine – I am not using any optimizer-plugin, just the actual twenty-twenty-one theme and the gutenberg editor – when creating a gallery the images do not appear on the final page as “blocked loading mixed active content” – following the link to firefox I did not find any further advice on how to proceed with images not being shown – as the same images do appear on other pages without the use of the gallery, I was wondering if the gallery itself might be the issue?

Any suggestions are warmly welcome!

All the best, Henry

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