This problem happened to me when I received an X1 TV Box in the mail to self-install. After plugging in the coaxial and HDMI to TV cable, I plug the power cable in. The TV Box would display the "Welcome. powering up, this will take a few minutes", then the "Welcome. connecting" screen, then it goes to the "We're updating your TV Box so you'll have the best experience possible" screen.. It counts down from 10 minutes, then it starts over again. It did this same cycle for hours.
Unplugging, waiting 10 seconds and re-plugging the power did not help. Sending a refresh signal did not help. Powering on without coaxial plugged then rebooting with coaxial plugged in did not help. I know that the power outlet and coaxial cable I am using should work because I previously used for an X1 DVR STB before setting up this TV Box. TV service on my account was active because I had access to Xfinity Stream services and TV showed up as a service on Xfinity My Account.
The problem appeared to be that the TV Box was not communicating with Xfinity . So it was not "updating" the firmware as it was supposed to. That's why it kept rebooting and failing to update. The Xfinity rep could not see my TV Box as "online" from her end. Steps I took to resolve the problem while the rep was on the phone.
1. Hold the power button in front of the TV Box for 10 seconds and let go (at this point error RDK-03003 showed up on my TV screen). Again, I previously had X1 working on this same coaxial, so it shouldn't be a signal strength problem.
2. Press the power button several times until the TV Box reboots.
3. Unplug the coaxial cable and plug it right back in. At this point the Xfinity rep could see my TV Box with "Online" status. The TV Box went through the same three boot screens again "power", "connecting", "updating". This time, the rep could also see that the firmware was being updated in real-time.
The TV Box went through the reboot cycle again, but this time it skips the "update" screen and goes to the setup screen. Chose the language, typed my last 4 phone digits to activate, and it continued to the loading screen.
I would consider that this whole process solved the "update" loop that it was stuck in. However, at the end of all the troubleshooting, the TV Box ended up being defective anyway. It went into an "This device needs to be initialized before we can continue" (Error XRE-00253) screen which requires a tier 3 service rep to activate the cable card. According to this other thread, https://forums.xfinity.com/t5/X1/Can-t-activate-PX022ANC-Error-XRE-00253-HELP/m-p/3025240#M143082.
The rep I was already speaking with told me that she has the authority to send an initialize signal to the cable card in my TV Box. We confirmed it was indeed the correct Cable Card serial number, DOCSIS MAC, and STB Mac numbers. However, after we waited for the entire reboot process again it ended up going back to the "initialization " screen again. She did also state that the TV Box was taking unusually long to get to this final screen.
In summary, all that time spent to get past the initial problem, time spent getting to the second problem to troubleshoot, I will end up having to swap out this TV Box at a service center for another unit.
I tried calling another rep later to see if maybe the first did not initialize my TV Box correctly, and to potentially save myself a trip to the service center. Turns out after this second rep checked (and also confirmed with a third rep) that the TV Box model I have, Pace PR150BNM, while it is modern for X1 service, there are known units out in circulation that have old coding on them that causes communication errors with the Xfinity service. Therefore, she also advised that the only remedy was to swap out the TV Box at a service center.
My gripe with this issue is why there isn't a QA person who double checks if these TV Boxes are fully capable of connecting to Xfinity service before mailing them out to customers for self-install. Nobody wants to go through hours of troubleshooting only to end up driving to a service center. This could have easily been a non-issue if it was confirmed working by Xfinity employees first-hand.
Hope this helps anybody else that runs into these problems. I did remember that the very first time I had an X1 DVR installed by the Xfinity tech in my house he also had to call the reps to initialize. So this seems to be a common problem for activating X1 TV service.