Unsupported Block Editor: Editor doesn't load on some Atomic sites on Android

[twstokes]

Describe the bug
On some WordPress.com Atomic sites the UBE fails to load. It will initially try to load, then show a message "Unable to load the block editor right now."

• Loading the editor does not fail on all Atomic sites
• On the Atomic sites that do fail to load on Android, iOS works

To Reproduce
Steps to reproduce the behavior:

1. Try to edit a post that contains an unsupported block
2. Tap the block to load the UBE
3. Observe that the UBE will try to load, then fail with "Unable to load the block editor right now"

Expected behavior
The UBE to load on all WordPress.com Atomic sites that use the Block Editor.

Screenshots

UBE.Android.mp4

Smartphone (please complete the following information):

• Device: Pixel 4a
• OS: Android 13
• Version 24.5

[fluiddot]

There's a known case on Atomic sites where UBE results in the error Unable to load the block editor right now: Editing unsupported blocks is disallowed on Classic-enabled Atomic sites. However, this should only apply on the following configuration:

• Classic Editor plugin installed.
• Default editor for all users set to Classic Editor.

@twstokes To confirm it's a different issue, I wonder if the problem you experienced on some of the Atomic sites might be related to this. Thanks 🙇 !

[twstokes]

To confirm it's a different issue, I wonder if the problem you experienced on some of the Atomic sites might be related to this.

Thanks for the comment @fluiddot! @geriux and I confirmed that the Classic Editor plugin was disabled (I also completely uninstalled it and retested) and all users were defaulting to the Block Editor.

ref: p1711121611565349/1710420260.200199-slack-C0126N6JH7Z