We have turned it(cdn) off, now. Now the error is gone. But the warning still stays there and no preview image is displayed.
Below is the warning I can see now. Not sure if its something relates to this
If you switch to Preview mode, does the block display correctly, with image?
Ignore those warning messages. If you look at the network tab, and find request that has Url as: Litium/app/api/websites/block/updatethumbnail/[block-systemId], what does it response?
Glad to hear that. Anyway, it should work without any issue with the default installation of Accelerator, unless if you have customized the way how Block containers are rendered. Please check the last section of the article https://docs.litium.com/documentation/architecture/blocks, where BlockContainerHelperExtension and _BlockContainer.cshtml are documented so you have a better idea of how blocks are rendered.