EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface
Deviation - Altitude Undershoot; Deviation - Altitude Crossing Restriction Not Met
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Aircraft; Human Factors
We were flying in VNAV cleared to cross BOONE at 11;000 feet.  11;000 feet was dialed into the altitude window; followed by /11000 entered next to the BOONE fix; activate was selected; 'pink alt' was verified on the PFD.  At some point after this we were asked if we had a lower clearance and I answered yes we [were] cleared down to 11;000 feet.  At this point I realized that we were almost to BOONE and still at 22;000 feet.  We looked at the MCDU and realized when the activate button was pressed it had not activated.  I know that the procedures were followed to correctly set up and execute a VNAV descent.  However; I should have been more thorough in my CAMI checklist.  The activate button was pushed but either not hard enough or it did not engage for some reason.  I should have and will be more vigilant in verifying the data entry.
We were flying in VNAV; 11000 feet was set and was put in the box; but it never activated. The button was pressed but it didn't activate; So the A/C didn't start it inital decent.
EMB175 Flight Crew reports being cleared to 11000 feet and setting up the the FMC and MCP to accomplish this clearance but apparently not pushing the activate button firmly enough. The aircraft remains at FL220 until queried by ATC.