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SB8200 failing but website says serial number not found

  • December 20, 2025
  • 4 replies
  • 115 views

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SB8200 failing but website says serial number not found
My SB8200 purchased in November 2021 keep dropping the connection since Xfinity upgraded things in the neighborhood. The connection keeps dropping. Xfinity says there is no outage. I've already upgraded the coax and splitters, etc. Still keeps dropping. It was running PERFECTLY FINE without a problem until they updated the neighborhood (Up to 10G). I cannot contact customer support due to the website saying my serial number cannot be found. I have tried entering it multiple times in different formats with no luck. To fix it, I just disconnect and reconnect the coax, and power cord, Then I am running fine for a day or so. Thank you!
 

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4 replies

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Could you please let us know the internet speed plan you are subscribed to?

To help isolate the issue, please connect any device directly and monitor the connection for 24 hours. By connecting the modem directly will help us to isolate the problem that if the internet drops on the Wi-Fi router or with the modem when connected to devices like a computer.

And checking the cable signal levels would be the best course of action as cable signal levels in modems refer to the strength and quality of the signals being received and transmitted between the modem and the Internet Service Provider.

Please find the below link, where you can steps to check the cable signal levels.

https://arris.my.salesforce-sites.com/consumers/articles/knowledge/SB8200-Cable-Signal-Levels


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  • Author
  • The Many
  • December 31, 2025

Fast Plan
Download speeds: up to 600 Mbps
Upload speeds: up to 35 Mbps

I use Moca inside the house, and xfinity put a moca blocker outside. 


What’s weird was we had no outages with the modem until Xfinity modified the network in the neighborhood up to 10G. I’ve replaced two coax cables inside. replaced a splitter. I’ve tried to add a automatic recycle at 3 am. 

 

It works for days at a time, and then there are a few days where it drops 5 times a day. I go back and check the cables, and reboot the modem, and after about 10 minutes, it works again. 

I even tried turning off Moca. I tried bypassing the splitter, so it goes directly from wall to modem. Doesn’t matter.

I’m wondering if the cable adapter on the sb8200 is faulty, I tried replacing the cable to the modem also.

I’m trying to figure out why the connection just randomly drops, and a 10 minute off and on, fixes it?

According to that link, I seem to be in range and acceptable. 

 


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As you mentioned, the issue began after your internet service provider upgraded their service in your area. Based on this, it is highly unlikely that the modem itself is failing.

Additionally, please note that the ARRIS SB8200 is not compatible with Xfinity MoCA networks. The modem should be connected directly to the coaxial cable from your provider, without any MoCA adapter in between.

We recommend checking with your internet service provider regarding the upgrade they performed.


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  • Author
  • The Many
  • January 6, 2026

Thank you for the response. It is interesting that the modem has recently not dropped the connection for about a week now. So maybe the modem was complaining about the noise outside of the house and they fixed the issue. I am not sure.

 

Second, you mentioned that the ARRIS SB8200 is not compatible with Xfinity MoCA networks. Can you please point me to documentation where it might have said that? If it is not compatible, is there a ARRIS modem Xfinity allowed, that is compatible with MoCA networks inhouse? I do not remember documentation anywhere on modem details that list that some don’t work with MoCA. Thank you for your time.