Grohe Tub spout diverter question
 

I purchased Grohe 13 628 Tab Spout with diverter for my new bathroom.
The diverter is a push button on the spout that has a spring and is
pushed down when water is running. The button is supposed to stay
pushed closing the tub spout and opening the shower. I cannot make this
work. As soon as I take my hand out of the button the spring pulls it
up thus opening the spout. Am I doing something wrong?