The Viessmann API has a limit of 1450 requests per day. The Viessmann integration uses 1440 of them, so there’s only 10 left a day. If you go over, you are blocked for 24 hours. This makes it pretty much impossible to do anything active with the integration, so it’s only really suitable for monitoring or very basic control.
It’d be good if it was possible to optionally increase the poll time, eg to every 2 minutes, which would give you over 700 requests per day, which would be plenty for active control. It’d decrease the responsiveness of the monitoring, but for many uses that wouldn’t really matter.