I unable to use my visual editor of gutenberg in my wordpress edit post/page. My wordpress installation in under abc.com/resources/ since I am able to use gutenberg visual editor on wordpress installation on abc.com

I am creating a dynamic Gutenburg block.

With the classic “Posts” post type, the featured image is saved, but not with custom post types.
Interestingly, when I pass show_in_rest to false(thus deactivating Gutenberg editor and switching to the classic editor), the featured image is saved when I publish.

I have three sites on a WordPress Network.
The first site is the master site and content is copied to the two other child sites.

I’ve created my wordpress block using:

i created a custom attribute with name “mediaItem“.

I quite like the core implementation of Expand on click in Gutenberg’s image block and would like to utilize it not only in posts created in Gutenberg editor, but also on other image elements. To be precise, there are plugins that still use TinyMCE classic richtext editor on some textareas and here the image element cannot be armed with built-in Expand on click function.

After having prefered to build classic themes for years (with good reason I’d say) I now about to dive deeper into the block-editor.
The kind of sites I mostly build need to get structured data and usually not a lot of ‘page building’ from editors that prefer a simple workflow. I accomplish this by using custom-post-types and (advanced-)custom-fields mostly.
Asthe classic-editor plugin starts to make more and more troubles (and feel more and more outdated) I am more or less forced to use the block-editor. (I#ve wored with it before, but without getting deeper into customizing/curating the editor/backend.)