Hello. I seem to be having the same issue. The assets show up when using the media library, but once I try to add them to an entry, they don’t show up. Interestingly, it happens only with assets that are in a folder.
I am using the strapi-provider-cloudflare-r2 plugin by @trieb-work so I am not sure whether it’s a Strapi issue or one by the plugin. Upgrading to the latest Strapi version (4.12.5) or downgrading to version 4.11.3 doesn’t seem to fix the issue.