Why isn’t the app connecting to the controller?
As explained in another FAQ, the app requires location sharing to add a controller. Otherwise connection problems will occur. If you have already granted location sharing, the automatic network change to the stronger WLAN network in the vicinity or to mobile data use may be the cause. Check under “Settings” to see which network your smartphone is connected to (see pictures at the end of the FAQ).
Some smartphones automatically connect to another network or the mobile network if no active internet access is available.
Solution: If it looks similar to the screenshot above right with the red X, deactivate the automatic network switch in the WLAN settings (usually a cogwheel icon). Another solution is to connect the controller to your home network as described in the instructions.