The heating plant is remaining off when the controller is in an occupation period.
The controller has shutdown because of high internal or high external temperatures.
The controller can generally be forced to night mode if one of the following settings is reached.
1 - Optimum Off - Minimum Inside Temperature - code B10
2 - Inside High Limit Temperature - code B12
3 - Outside High Limit Temperature - code B14
In the case of item 1, if the controller has decided that it can optimise off, then this setting is the lowest temperature before the plant will be switched back on again.
Items 2 and 3 dictate the temperature above which, the plant is switched off.
If the plant has switched off then changing the appropriate setting will allow the plant to switch back on again.