Delonghi EC702: Latte works, espresso is defunct. Pump problem?

We have a DeLonghi EC702 espresso machine. Its "latte" function works, but its "espresso" doesn't. My observations of its three buttons and their indicators:

I turn the machine on (depress top button, top LED lights red) and wait 15 minutes until it's fully heated (middle LED lights green).  When I depress the middle button, which should run the espresso system, nothing whatsoever happens: no sound, no sign of any action.  When I depress the bottom button for the steamer (bottom LED lights red), and I turn the knob to release steam, it works correctly.

As far as I can tell with a circuit tester, the middle button's switch is working correctly. But I'm not completely certain of this; it's a bit tricky to be probing within the case, and I'm reluctant to disassemble the thing enough to isolate the switch without need.

Is this likely to be a pump problem? An electrical failure? Do such machines use separate pumping systems for the espresso and latte outputs?

Thank you for any advice.