A very common cause of not heating in Miele dishwashers is the high level pressure switch not operating. Usually you can hear the operation as you start and stop the dishwasher with water in it – if you can’t hear a faint click then that is the culprit. There are several different versions of this switch – three listed as curent for the model you posted – so the ‘T’ number off the old switch would help.
There are 2 pressure switches in the machine, the one for overfill detection has a small hose connecting to the bottom of it and the one for heater operation has a larger hose connecting to the back of it.