I spent hours trying to finalize trade in of my device because I purchased my phone, then did the trade in later as it was missed with the over the phone order.
Solution: Do not Choose Verizon as the carrier when going through the trade in process. Instead, Choose 'Other'
After I did that I was able to get a submission ID and was good to go.
Online or phone support could not figure it out. After persistence and trial and error, I figured it out.