This procedure worked for me to reconnect your I-Pace to the Incontrol Mobile app.
(1) Sign in to your Incontrol Account by opening your browser to https://incontrol.jaguar.com/
Do Not use your Mobile App for this procedure!
(2) Click on "My Account" on the upper right portion of the main header.
(3) On the left side of the new window, Click on "All Device Signout." Make sure you have your Incontrol account log-in and password written down. When the page refreshes, click on the red button "All Device Signout." Doing so will sign you out of your Incontrol account across all of your devices.
(4) Sign back into your Incontrol account via a browser. Hopefully, you wrote down your log-in and password.
(5) Click on "Vehicle Settings," on the upper right portion of the header, just below the heading "Help, My Account, Sign Out."
(6) Click on "Remove Vehicle" on the left side of the window. When the page refreshes, click on the red button "Remove Vehicle." Doing so will delete your I-Pace from your Incontrol account. You will receive confirmation, whether you are successful or not.
(7) Once step (6) is successfully completed, click on "Add Vehicle" on the left side of the main header. You will be now begin the self-install process of adding back your I-Pace to your Incontrol account. *Before beginning the process, make sure to turn off the I-Pace's WiFi connection, verify your I-Pace has good cellular connection (main I-Pace screen, icon in upper right hand corner), have your VIN handy, and have your I-Pace nearby (you will need to access it and press the "Optimized Assistance Button" on the left side of the overhead console). Once the process begins, you'll have 60 minutes to complete it or you'll have to start (7) all over again.
When instructed to do so, here is the process for pressing the "Optimized Assistance Button:"
Quickly press and release the small panel covering the "Optimized Assistance Button" to expose the actual button with a amber LED light.
How long should I press the “Optimized Roadside Assistance” button for?
Press and hold the “Optimized Roadside Assistance” button. After a couple of seconds the button will flash amber quickly. Continue holding the button for 10 seconds until the button flashes at a slower rate. Release the Optimized Assistance button which will continue to flash slowly for a short period of time. After two seconds the button will go out completely.
(8) If step (7) is successful, you'll be notified. If not, try repeating step (7).
Hope this works for you...