Please be advised there are two options to update Sold listings to Settled.
Option 1: (Recommended)
Go to Each Sold listing and add a Vendor if one has not yet been added.
Click on Edit Contract and enter in the details of the sale including the contract and purchaser details.
Once all details have been entered, you will be able to save the Sold listing and then updated to Settled. This will then also create a new Prospect listing with the Purchaser as the new Vendor.
Option 2: (Quick Fix)
Go to Settings > Import Tools & Logs > Sold to Settled
Tick all listings you wish to update to Settled and ensure that the Settlement Date is correct for all listings before clicking on Save.
Please note that this method will not create a new Prospect listing however you can clone the Settled listing/s.