The provided edit sequence is out-of-date.

In your error log after a sync, you might see a message like the following: "Error 3200 : While trying to Mod a(n) Customer with name or order number of , QB responded The provided edit sequence "1554215500" is out-of-date."

This typically happens during a sync when a customer has an invoice, sales receipt, or other type of modification occur before being updated. We attempted to modify the customer record afterward, and causes this error since the object is no longer up to date.

Solution: 

Go to Settings -> Customer Matching and uncheck "Update customer contact info in QuickBooks"