Why am I get error "NOT SOLD, NOT IN STOCK, NOT REGISTERED" when trying to invoice a vehicle?

Sales Order Verification:

• Ensure that a sales order is associated with the vehicle.

Stock Status Check:

• Confirm that the vehicle is currently in stock.

Registration Details:

• Make sure that a registration number is entered on the deal.
• For new, unregistered vehicles, you can enter "TBC" in the registration field.