You have to create a program adding the zone, the time frames and the days you want to water. 

For instance: Program 1

Zona 1

From 9:00-10:00

From 13:00-14:00

From 18:00-19:00

And check Monday, Wednesday and Saturday. 

If I were you I would double check the physical connections. Maybe you can try to move the cable from zone 4 to one of the zones that are working (i.e. zone 3) to discard any problems with netro in port 4.

if the problem persist, that means that Port 4 is not the problem, then I suggest to use a multimeter to verify again the connectivity between netro and the valve.

Have you already verified that the problem is not the lack of water, right?

Good luck!

me respondo yo mismo a mi mensaje para informar a todos: Recibí una respuesta del fabricante indicando que no es posible poner dos zonas en paralelo, así que he tenido que modificar mi instalación de riego a nivel del cuadro eléctrico para solucionarlo.