If the internet light on the modem is OFF that shows the modem is not getting IP from the service provider or that might not the valid IP address so to isolate the issue we would suggest you to try checking the IPV4 address on the device connected to the modem LAN port. So First if you have router connected to the modem ethernet port disconnect the router and then power cycle the modem for a minute, after modem reboots completely you can connect device like laptop or computer to the modem then check IPV4 using command prompt.

Thanks for the response. After discussing the matter with both Arris and Xfinity, I discovered the likely cause is that Xfinity has chosen to throttle the speed it delivers to the SB8200 and my current internet subscription exceeds the limit. Despite the SB8200 being able to receive up to 2Gigs (per packaging), Xfinity has chosen to throttle the speed the Surfborad can receive to 800Mbps. Since my plan is currently providing 1.2Gigs, either I have Xfinity reduce my internet speed so the Surfboard can be used (no thanks), or I remain hostage to paying the monthly rental fee for Xfinity’s modem.

Seems to me Xfinity is protecting its own self-interests by choosing to throttle competitor’s modems, which makes sense for them, I just wish this had been advertised better before I purchased the Surfboard and additional router thinking the higher upfront cost would pay itself off over the long run of not paying monthly rental fees. Turns out it was all just a waste of $ and I should have just stayed with Xfinity’s rental from the get-go.

TAKEAWAY - Just because it’s “compatible” or “approved” by your ISP, doesn’t mean it’s going to work. Call your ISP first before purchasing a modem to see if they’re throttling the speed to the model you’re considering before you purchase.