Connection problem

[CrewMom9]

My son sent me his modem for us to use (he lives in Idaho and had been using it on his Sparklight account, which he has closed in order to use a fiber optics account elsewhere).  We live in Jacksonville, FL and we are trying to use this instead of renting the equipment from Comcast.  I have spent hours on the phone with Comcast and I have also called Netgear.  It seems that the MAC address for this modem is listed in the Comcast Xfinity system, but not associated with any account.  I cannot connect this modem and I don't know where to go to find out where it might be registered, listed, etc.  I am at a complete loss for what to do next in order to use Comcast Xfinity's internet without their equipment.  Has any had any of these issues and, if so, how did you solve them?  I don't want to have to go out and buy a new modem when this one is fairly new and it would work fine.  I would love to hear what my next steps should be in order to get this unit connected and up and running.  Thank you.

[FURRYe38]

Factory reset the modem. Press the reset button for 15 seconds then release. You'll need the ISP online and have them help you re-associate the modem with there system to be sure it's online with there services. 

Have the ISP check the signal and line quality UP to the modem. 
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.

IF you have a wired PC connected to the modem directly, it should get internet services after the reset and setup with the ISP services.

Be sure you power OFF any external wifi routers connected for 1 minute then back on, between the modem and your PC. 

[CrewMom9]

Thank you for your reply.  My son had me hold the reset button on the modem - I was not online with my ISP provider.  I spent hours ad nauseum on the phone with Comcast and they still see the MAC address somewhere.  I am hoping that it will take a couple of days for the company that my son used for his ISP to purge their system and then Comcast will not see it.  I really, really do not want to go out and buy a new modem since this one is more than adequate.  Comcast is going to call me back on Tuesday to see if the modem is available to add onto my account, so I need to get some patience.  I will see if we need to follow your advice - right now I have had to disconnect that Netgear modem and reconnect the Comcast equipment.............I will try to update things when I hear back from Comcast and I will ask them about your suggestions as well.  Thank you.

[FURRYe38]

SparkLight should matter if they had the MAC address since its a different ISP service and isn't on CC system or releated. Odd that the MAC address isn't being seen on a different ISP service. I guess have your son contact Sparklight to have them remove the mac address from there system. Hopefully the modem doesn't have to be connected to there system to get removed. Shouldn't. I on SparkLight as well though I haven't tried using a modem on a different ISP system. 

Hope something will get it working. 

[schumaku]

Look here: How do I activate my Internet service with Comcast XFINITY? 

[FURRYe38]

The URL doesn't seem to be valid or working. 

Please do not use this link. I would avoid trying it.