Apparently Google can "forget" to register devices on a carriers which will mean there will be a 1 to 4 days activation time after you get your phone. If you had a backup device and turn it off before you power on your Pixel you got in the mail, then power on your Pixel it will not activate. Mine kept saying something about needing better coverage to activate. Then it said an error happened during activation and I needed to call customer care. So basically they have to put in a request to Google to activate the IMEI on Verizon's network (Make sure you give them the right IMEI & SIM #) which will take some time. The associates I spoke to didn't seem like it was a rare occurrence for manufacturer warranty replacements.