Vev Vigano Vespresso Stovetop Coffee Maker malfunctioning

I bought a fancy 4-cup Vev Vigano Vespresso stovetop espresso maker a few weeks ago. I had to upgrade from a Bialetti-style coffee maker after its handle broke off. Sadly, I have not figured out how to get this coffee-maker work. Though it has made tasty espresso on a couple of occasions, these seem accidental. It hardly make a single full cup of espresso most of the time, and struggles to do so (spouts and makes noise and squirts the coffee out sporadically instead of making a longer stream of it).

I have been watching videos and trying everything--desperately. Medium heat, higher heat, coarser grounds, finer grounds, less coffee, more coffee, tamping it down and not tamping it down. I always make sure not to fill water above the pressure valve. I have never gotten 4 cups out of it, and don't get what's going wrong, it's sort of driving me insane. I saw great reviews for it everywhere and I doubt it is defective as it is a simple mechanism and I checked every component of it.

Could anyone give precise advice on how they make it work? Most of all, how coarse their coffee grounds are, how much they fill the little funnel, and whether they tamp it down (if so, how) or not. Please help me get my money's worth out of this machine!