@Hank434
Welcome to the community.
There are some detailed suggestions for your reference:
https://www.tp-link.com/en/support/faq/2239/
1. Disable Bluetooth and then enable it again on the mobile phone. If there is a Bluetooth device connected to the phone, please disconnect it temporarily.
2. Force the app to close (do not let deco app run in the background), and then launch the app to configure the main Deco again.
3. Use another Deco unit as the main Deco; use a different phone to configure Deco if you have one.
Note: For iOS 13 or higher version devices, please go to Settings on the iOS device, find the Deco app and enable the Bluetooth permission for the Deco app.