In case of any changes to an existing Item/Customer/Vendor/Account, you may see this error message while posting data to QuickBooks. We would need to refresh the database on Webgility by downloading the latest data from QuickBooks.
There is an invalid reference to QBs items in the sales receipt line: QBs error message: Invalid argument the specified record does not exist in QBs
Login to your QuickBooks as the admin user, and if possible switch to single-user mode.
Navigate to Integrations > Stores > Advanced Settings.
Click Clear for the Last Download Date for QuickBooks Item and the Last Download Date for QuickBooks Customers as per requirement and click Save and close the screen.
Now, download data by going to Integrations >> Get the latest data and settings.
Click on the drop-down associated with the Download Data button and click on Re-Download All Data. The process of downloading data may take a few minutes depending on the volume of data in your accounting file.
Once this is complete you will be shown a message indicating that the download was successful. Now try posting orders to QuickBooks.
If the issue persists, feel free to open a Support chat.