It's lost its prime. I actually had a similar problem with a similar machine design: water flows via gravity (and pump suction) through the outlet valve in the bottom of the removable tank into a very small intake opening in the tank receiver base of the machine and is then drawn into the pump via internal tubing. If the pump loses its prime and becomes filled with air, it has little or no suction power to draw in the water. Gravity feed alone cant provide enough water pressure to reprime the pump. You will need to somehow provide water pressure into the inlet hole with the pump running to get it re-primed. Here's a suggestion for doing that.
For the record, mine was a brand new Capresso EC100
It had lost its prime as well. Just loudly pumping air and not drawing water from the tank.
A turkey baster was too big for the tiny inlet hole, so I used a Dental Irrigation Syringe I got from Amazon. I inseted the long ,narrow curved nose down into the hole with the pump running and injected water. There finally was a loud slurp sound and it began pumping water!
So happy I found this suggestion here and could avoid a return and time on the phone with customer service.