Why can't I heat water properly on a new glass cooktop using a stainless steel pot?
One possible reason for this would be if the cooktop used induction, where rather than heating up, it used electromagnest to cause the pan to heat up.  For this to work, the pan must be ferrous and able to be magnetized.  Although stainless steel is made from iron, it isn't strongly magnetic, and thus will not work well on an induction cooker.

To test if this is the case, you can try pans from other materials and see if they have similar problems.  Aluminium, copper, or ceramic cookware simply won't heat up at all.  You can also try turning an element on high without a pan, and waiting a minute or two.  If you can hold your hand above the element without feeling any heat, it's either an induction cooktop or defective.

If you place a cast iron or carbon steel pan on the element, wait another minute or two, and test again but can feel heat, then it's induction.

As you mentioned it's a new cooktop, if it's new because you bought it (and not because you've moved), find the manual, and if it's an induction cooker, it should proudly proclaim that fact, and list what types of pans are recommended.

...

The next possibility is that if you're coming from a gas cooktop you may not be used to the speed of electric cookers.  With a glass-topped cooker, it's difficult to see the size of the elements, and so you may only have one or two elements on the cooktop that are rated for fast boiling or other high-heat applications.  You can try each of the burners in turn, and see if some of them heat up faster than others.

... but there's also a chance that the element is defective.    I'd suggest calling their customer service number, or e-mailing them to ask about the cooktop.