Each of the devices that are the part of ViCare Smart Climate program communicate with each other via radio signal. When the internet connection is lost, the devices are still able to communicate with each other. You will not be able to change the temperature values and Time Programs (schedules) via the ViCare app, but all the previously defined settings are still in use.
When the internet is online and working and the devices don't read the changes you made via the ViCare app, it means that the radio signal is blocked or switched off. If the devices were operating correctly before, please check on the boiler or heating device display panel if “Low Power Radio” is turned on. For Viessmann One Base systems, you can also find this information in the ViCare app in the “Settings” section under “Communication module”. To assure trouble-free operation between devices, the radio signal has to be switched on.