There have been a handful of Attachment Viewer questions already (here, here, and here, but none seem to capture quite the behavior I'm seeing.
The "No Attachments Found" error is only occurring for Community accounts. The applications works fine and displays attachments for anyone with a regular organizational account with access to the group where the application lives. However, if one uses a community account to access the application they'll have access just fine, but they'll see a "No Attachments Founds" error.
If logged into a Community account, however, one can navigate to the group, the layer which is used in the app, and then view the attachments in the Data tab, so it doesn't seem to be an issue with access or credentials, per se.
I would like to know if there is a workaround or if the product is non-functional at the moment, as we'd like to keep using our community accounts for this purpose.
Paging @RyanLibed, @KellyHutchins or @ManishPatel, who seem to be familiar with these issues from previous threads.