Hi there,
indeed, Google removed the app from the store a couple of weeks ago, due to a problem with the login and the privacy policy. The app has to be updated to display the privacy policy before the user performs the log-in or something like that.
I haven’t had time yet to adapt the app to the new Google guidelines. In the meanwhile, you can download it directly from here:
https://www.smart-thermostat.eu/wp-content/uploads/2021/08/app-release.apk
And now, about the main problem. Indeed, a couple of days ago, the backend was moved to a new server. I have reviewed the logs of the server and didn’t find an error or something that explains your issue.
Because of that, I need to ask you for more information. May you install a network tool app, like for example,
https://play.google.com/store/apps/details?id=ua.com.streamsoft.pingtools
on both of your devices (the thermostat and the client), and ping the following url: https://www.smart-thermostat.eu
The IP returned should be 144.91.89.223. If it is not, then you have to force your device to refresh the DNS. This can be achieved by rebooting your devices or rebooting your router.
Please let me know if this helps. If not, we will look at it in more detail.
Thanks!