This is one of the most common errors experienced when you first attempt to sync revenue using Wise-Sync, this is due to the additional required information not being passed through to Xero.
When the Non ProductID is omitted, then the following error will result:
No Item ID or Non-Product ID has been defined in ConnectWise for an item with Account Number '[your account number]'.
Why is a Non-Product ID Required:
The notable difference between revenue from Products and non-products is that Wise-Sync will require a Non-Product ID in order to post service revenue. Including this helps by using inventory items for these revenue lines, allowing you to run reports for inventory items in xero. This can provide effective segmentation by using different non-product ID's for your revenue centers.
Refer to the following KB Article: Setup Connectwise > Step 8 > GL Mapping (Non-Product Revenue & COGS Accounts)
An omission of the Non ProductID for revenue which is not related to Product sales requires that a Non-Product ID is passed through to Xero when the revenue is being posted via an Invoice.
The types of Revenue that require a "Non ProductID" for each GL Mapping are: