Why the Sync Error occurs
This error occurs for one of 2 reasons:
When you link a bill to a PO in Oracle NetSuite, and that bill tries to sync to Bill.com, but a line item(s) amount on the bill does not match the line item(s) amount on the PO in Bill.com.
When you link a bill to a PO in Oracle NetSuite, and that bill tries to sync to Bill.com, but the PO has expense line items in Oracle NetSuite. Bill.com does not support linking bills to POs that have expense line items.
How to Fix the Sync Error
Edit the PO or the bill in Oracle NetSuite so all lines on the bill have the same amounts as the lines on the PO, and sync again.
Since Bill.com does not support bills linking to POs with expense line items, the bill will remain unlinked from the PO in Bill.com, but it will stay linked in Oracle NetSuite.
You can still pay the bill in Bill.com, and the payment will sync to Oracle NetSuite and mark the bill as paid.