You're not alone with this problem. I had similar a few weeks ago. All the lights on the display would come on but when pedaling the side indicators to show amount of peddle effort and battery effort would not display and no power.
It was suggested that after removing and replacing the battery that the pins taking the power to the motor were not contacting (the pins are spring loaded) The first solution was to tap around that area with a hammer. That worked -----for another 4 rides. I had my reservations about that explanation because The bike would "walk" when the Walk button was pressed.
Another more believable suggestion was that the torque sensor had failed. A couple more taps (with a rubber tyre mallet) worked again. At that stage the bike went back to the LBS and on return has worked. One ride so far. Had different advice as to what was done and don't know what to believe.