My original 3xl had an expanding battery so Google replaced it (purchased through Best Buy). That replacement activated, but after a handful of days wouldn't stay connected to Verizon's network (would connect for a short time, then disconnect and would keep cycling through that behavior). I visited a Verizon store and after they called tech support, it was determined that the replacement wasn't compatible with Verizon's network (the IMEI wasn't in their database -- something like that -- and nothing could be done about it).
Back to Google, they replaced the replacement with a different refurbished one. Again, activated just fine. Verizon sent an email asking to verify that the sim was moved to a different device. Went to my account and, same problem; Verizon indicates that this different device isn't compatible with the network (yet, at the moment seems to work just fine -- same as the first replacement). Sure enough, when looking at the devices on my account, this one shows up as a "null phone" and the model isn't noted.
As an update; found an old post in a Google forum that sort of points to a potential snag where Google sends an RMA device that's intended for Google Fi (findable by looking at the user agent when running a search via google). That post implied that there are 2 variants; one for Verizon and one for Google Fi. What I see is that the replacement device I received appears to be the Google variant. <sigh>
Thank you for reaching out to us today. We definitely want to help look into this further. Please send us a Private Message so that we may help by reviewing the details in your account.
Glad to learn that the device is working the way it should be on the cellular network. Please let us know if anything changes.