Worcestor Greenstar Boiler/Smart thermostat

BUFF

EMS bus is Worcester's advanced communication protocol between boilers & thermostats. It is very similar to (but not the same as) Opentherm.

Modulation is where a boiler rather than simply turning on/off adjusts it's output to demand - it is more efficient & better from a wear & tear pov. https://www.heatgeek.com/what-is-boiler-modulation/
If your stat supports an advanced protocol then it allows more accurate control https://theevohomeshop.co.uk/content/21-What-is-OpenTherm-and-why-use-Honeywell-evohome-with-it

If you have a condensing boiler capable of modulation/load compensation but the thermostat can't communicate fully with it allowing modulation/load compensation then it will work as a simple on/off stat so your boiler won't be achieving max. efficiency.
The likes of Nest, Tado etc. can't atm communicate natively with WB's EMS. The DT20RF looks remarkably similar to a Drayton LP20RF - I imagine that it is a badged version of the Drayton - so hopefully Drayton has a good chance of being able to enable EMS in Wiser unless there are contractual reasons not to.

As of today Wiser support has not replied to my query.

BUFF

Drayton Wiser replied to me today - Wiser does not support Worcester's EMS (but does support Opentherm).

VT41

So.. I’ve had the thermostat installed. 

The hub connected to the boiler, room thermostat in the hallway  and mobile app

I can control the heating via the app, manually turn it on also on the hub but having issues amending the temperature etc using the room thermostat. Seems to be a connection issue between the room thermostat and hub. 

Tried resetting (taking the battery in/out) and holding the + and - sign. Anybody has similar issues?