Why an order was not updated
The cases where the connector refuses to change a sales order, and where it writes the reason.
Refusing is deliberate
The connector refuses to change a sales order when doing so could corrupt existing accounting or stock documents. The caution is intentional.
When an update is allowed
It is allowed when the sales order is a draft or a quotation. It is also allowed when it is confirmed, provided it has no invoice, has not shipped, and no stock picking has been validated.
When it is refused
It is refused once an invoice exists, or a stock picking has been validated, or the sales order is in a state that does not permit changes.
Where to find the reason
The connector writes a note in the Chatter on the Odoo sales order explaining exactly why. Open the sales order and scroll to the bottom.
It fails safe
If the connector cannot verify the state of the stock pickings, it refuses rather than risk it. This is on purpose: refusing is safer than damaging a document.
What to do about it
Edit the sales order in Odoo by hand, or cancel the related documents and re-sync the order. See Re-syncing an order in the Orders section.