As you may know, Yonomi controls some devices via the local network instead of via cloud APIs -- this include devices like Sonos and Wemo.
For actions run directly from the app, we can send commands straight from the phone to the Sonos or Wemo over your local network, but for commands sent via other interfaces (like Alexa), we have to send commands down via our own cloud platform to your mobile device and we do so with push messages that sometimes can be a little less-than-reliable.
If actions for your Sonos or Wemo are not running consistently from Alexa then it may indicate that your phone may not be relaying the messages to the devices.
Given that, here are a few things to know and try: In order for us to deliver a command to devices like Sonos and Wemo your phone has to be joined to your Wifi network and the Yonomi app has to be running. It's OK if the app is in the background and if your phone screen is off but the app just can't be completely killed. If the above conditions are correct but it's still not working there are a couple of other things to check. Please ensure the following are enabled for Yonomi on your iPhone: Notifications (via Settings > Notifications) and Background App Refresh (via Settings > General > Background App Refresh). Lastly check to make sure that your phone is not in Low Power Mode(Settings > Battery). Give those things a try and let us know if that helps or provides any improvement.
Thanks,
Yonomi Support