Heating won't go off?

Hello can someone please help me? I have a Siemens RDJ10RF unit configured to a Baxi boiler.
The timer isn't working at all. I'm having to turn the unit off to turn the heating off, but when I switch it to auto the heating comes does on, but unless I turn the unit off the heating is on constantly. I've tried resetting etc, the vertical is set to run and the horizontal to auto. Just don't know why it won't reset?