Scenario:
A Bill was created and submitted for approval in Xero.
Attachments that get added to that Bill at a later stage (usually via an OCR solution) don't show in ApprovalMax.
Reason:
Unfortunately, an attachment itself does not trigger a document update in Xero. Therefore, such a change (i.e. the attachment) does not get synced to ApprovalMax.
Solution:
Open the Bill in Xero for editing and click on SAVE.
Now, the change in form of a new attachment will be synced to ApprovalMax.