Can control a device via developer tool, not via homey app

Hi. I have a homey 2016-2019. Since a couple of weeks I cannot controll a device (smart plug switch Z-wave) from the homey app or my.homey.app anymore. Not via a button, not via a flow. But I can manage it via the Homey Developer Tools page (send basic on/off). How can I fix this? I tried to update the route as well, but that didn’t work.