I just disconnected my number from Synthflow and switched it to Vapi - but when I call the number I am getting a message: “We are sorry there has been an application error”. I checked the logs and its retruning a 404 error. I did some more troubleshooting and added my "MyTwillio Number" phone number (from the Twillio Account Dashboard) and the call worked. Both numbers have the Vapi API URls in the Twillio configs. Not sure why the primary phone number is working but the other number in my Twillio account isn't. Please help. I even tried using the phone number's SID (the phone number I want) and it didnt import.

your secondary isn't linked to vapi correctly. import it first and then ensure your twilio configs are same as primary phone number it will work

Its connected right now

yes try this.