The electronic solenoid valve is not working.
Some points to consider:
•  Work through the Delabie Installation and Technical manual.
•  Check that the solenoid valves have been fitted the right way round.
•  Check that debris has not washed up the water supply line(s) and become stuck in the valve.
•  Make sure that the filters are fitted.

My mixing valve is not operating properly. The water won't come out correctly.
Be sure the mixing valve has been installed correctly on the water line. Where it's marked EF (or CW), should be connected the cold water line; where it's marked EC (or HW), should be connected the hot water line; and where it's marked EM (or MW), is where the mixed water should issue.

For Example:

For battery-operated taps, about how long should the batteries last?
Batteries are estimated to last from 250,000 to 300,000 uses.

On Tempomatic Knee-Operated Valve Models: 735 400 & 734 100, can the valve be shortened?

Yes. Knee valves can be cut up to 200mm off the original size. The diagram below illustrates this action.