If you get or receive the follow error or exception, check the solutions shared.

First exception on row 0; first error: FIELD_INTEGRITY_EXCEPTION, field integrity exception: unknown, unknown (versions 3.0 and higher must specify Pricebook Entry Id, others must specify product id): unknown, unknown

Solution 1:

http://help.salesforce.com/HTViewSolution?id=000166658

Solution 2:

Make sure while creating OpportunitLineItem (Opportunity Product), PricebookEntryId is not null.

Please don’t lower your API version since the legacy API versions will be retiring soon.