Object owned by another entity, operation not permitted
This error occurs when updating a bill in Bill.com. The bill came from Sage Intacct and the origin of the bill was a Purchase Order. You can't edit bills that originated from Purchase Orders in Bill.com or Sage Intacct.
To update bills that originated from Purchase Orders, you have to update the actual Purchase Order in the Purchasing Module in Sage Intacct. This will update the bill in Sage Intacct, and then the sync will bring the update to Bill.com.