How to update the Product’s Unit Price in Salesforce from QuickBooks  Items when a product is associated with multiple Pricebook in Salesforce.

Issue: 

Error 'Field integrity exception' when you update the Pricebook Entry object via API

Description:

When you attempt to mass update the Pricebook Entry object with Data Loader or other API tools, the error "field integrity exception" is received.

This is because the checkbox 'Use Standard Price' is checked on the Pricebook Entry record. This means that the field becomes unavailable via the API with exception of the ability to update the 'Use Standard Price' field itself.  

Solution:

To resolve this issue, update your PricebookEntry records and set the "Use Standard Price" field to false before you attempt to update product's unit price.

After uncheck the 'Use Standard Price' field in Salesforce, then try to update the unit price from QuickBooks to Salesforce through API Integration.