New Equipment Activation

Good Morning, 

Service went out yesterday morning, (ingress issue), in the meantime as I had an older approved modem (Motorola SB6121) that's no longer on the approved list, I figured I'd get a new one that was on the current list to take that out of the equation(Motorola SB8200), After phoning business support to have the modem activated, service was still down.  Luckily tech was already on the way.  Found person I spoke to didn't record the new modem info and/or activate the modem. (Old modem MAC address only registered modem) Were a few other problems that have been rectified, however, the SB8200 is having issues recognizing docsis 3.1. (known issue, spoke with Arris, and Comcast irrelevant) As I don't have the time to continue to deal with this, I've purchased a Netgear CM1200 (on the approved list) and will need it activated when I pick it up later this a.m. My question is, am I able to use the Xfinity "gateway" for activation(online) or is there a faster way to get the modem in Comcasts system versus calling support?  The tech texted the info and seemed to have it registered and working in about 10 minutes... Thank you in advance.