THE WATER FLOW DIVERTER OF GEMMA DOES NOT WORK PROPERLY

Very likely the hose connecting the shower panel to the mixer has been exchanged with the hose connecting the shower panel to the showerhead.

The hose with the smaller thread (3/8'') must connect the panel to the showerhead, while the hole with the bigger thread (1/2'', not included in the packing) must connect the panel to the mixer.