Basically any room stat is just an on/off switch regardless of how clever it
appears to be.
Whilst not familiar with your model most stats when removed from their
backplates disconnect from the system.( when you take it off ,no wires are
If this is the case then the programmer is wired wrongly.
From your post it seems the system works fine if on 'Timed' but if set to
constant the stat does not work.
Again suggesting a programmer fault or wiring fault at the programmer.
To verify run the system on constant ,remove the stat (turn off power first
it may be mains switching) make sure no wires are connected to the stat
,insulate any bare wires ,return power .
If system still works the fault is either in the programmer or a secondary
We really need more information for further help.
What type of boiler do you have ?
What type of system (fully pumped 'y plan' etc)
What programmer controls the system?