20 bought only 16 operate

I bought two sets of 10, so 20 units to mark (1 every 3 m) aisle 60m of the portal to the terrace, I have put all units ON (because they are all in OFF boxes) and waited three days of full sun to put my comment and I am not satisfied because only 16 operate in the 16 and only 12 remain on at 6 o'clock when I get up.
Briefly they are not expensive perhaps, but not good for over