Before you start, a few things will be required to follow the steps.
When Duo tries to authenticate (do not authenticate), select Other Options
Select Manage Devices
You will need to verify yourself. Select Text message passcode.
Enter the code texted to your smartphone in the passcode field box. If you do not get the passcode, select send a new passcode and enter the code sent via text.
Once verified, you will see a list of devices on your Duo account. Select I have a new phone (or Add a device if you don't see your number listed) under the device phone number you need to reactivate. Note: Device type (Android, iPhone, etc.) will update after you reactivate your new smartphone.
Select Get started on the "Let's set up your phone" screen
Select Send me a passcode to confirm ownership of the smartphone
Enter the passcode texted to your device and select Verify
If you get an error that says to contact IT, select Back and try again