On the CI Pad: go to Carpe Manager – App Shelf and make sure you have the latest version of the Controller app. (The list of versions is here: https://carpe-iter.eu/blog/controller-app-updates-change-log/)

On any other Android device: go to Google Play store, find the Controller app by Carpe Iter and see if the button says Open or Update. You always need to have the latest version.

After that, for all devices: Pair it manually via System Bluetooth settings. Make sure the intended controller is the only one paired.

Open the Controller app and follow the instructions.

If there was an issue, go back to the Bluetooth system settings, tap the paired controller, and select “forget”. Then repeat the whole process.