Hope this helps someone. It has been over a week and easily 8 hours of setup time. BTW, I'm an engineer.
This morning after wasting hours on the phone, I went on the "chat" help and "Rowena" had me activated in roughly 15 minutes. I'm bewildered but happy to be able to watch tv although there is still no sound.
Third phone call, got Carlos, went thru whole process again, computer says "activated" but TV says NOT AUTHORIZED to use. Carlos puts me on hold for 30 minutes scheduling someone to come out - at my expense I'm sure. NO call yet to schedule tech. SEVEN DAYS later, no TV! Walkin to phone now for call #4.
Sounds like somebody has the box numbers wrong. Might want to check you account on-line and see if they have the correct numbers entered. Pretty unlikely that two HD boxes would both be bad (but not totally unheard of). After confirming the numbers are correct (and trying the activation yourself) call 1-800 Comcast during the day. If things still don't work you may want to either have them roll a truck for you or try another two boxes?
Sending my standard def box back, sprung for two HD boxes @10bucks/month, followed activation steps, got NADA. "This explorer box NOT AUTHORIZED for use" call 800-India. So I call the number and the very polite and well spoken guy does some "resets" remotely. NOTHING. Has me pull plug. NOTHING. Has me wait a few hours. Left it on overnight. NOTHING