Due to certain issues on Facebook’s side, Regular buttons may not work on Android devices with the Attachment Unavailable error. You can track this bug’s status in the following threads on Facebook:
https://developers.facebook.com/support/bugs/984268978897137/?join_id=f18a3f0f5cbc228
https://developers.facebook.com/support/bugs/554534385937462/?join_id=f19795bdef9b884
More information to follow soon.