I pressed the power and the Brew button simultaneously and now the system seems stuck on

Pressing the Power and Brew button together puts the system in the descaling mode (a 10 minute cycle).  To exit it, unplug the system, plug it back in, place an empty cup on the tray, and press and hold the brew button until you hear the long beep (~3seconds).  The system will drain any water that was loaded into the boiler.  At that point, the system will be ready to use again.