TLDR; If your S33 isn’t working to connect to the internet, the modem itself is buzzing, the light cycles between amber for a while then a quick change to white/green and then off only to restart the cycle, you may just need a new power adapter to get it to work again.

I’ve looked through several posts of the same problem I was having starting today. The modem was buzzing and there was a constant cycle of the lights no matter what I tried. The amber light was on for about 7-10 seconds and then flipped to a white/green light for a second or two before turning off and then restarting the cycle of amber, white/green, and off. Things I tried to get it to work include disconnecting and reconnecting the power to the unit, confirming that my internet service provider (Xfinity) had no reported outages, removing the coaxial cable, and attempting to reset the whole modem. When I tried resetting the modem with the reset button on the bottom, nothing happened regardless of how long I held the reset button for. The buzzing and the light cycling would happen instantly after disconnecting and reconnecting power.

I spoke with customer support who walked me through everything to try and figure out what the problem was. Even when connecting via ethernet to my computer, there was no IP address given. We were on the verge of considering the modem faulty (under warranty) with a plan to send out a new one. However, there was one more suggestion to try using a different electrical outlet and trying a different power adapter. I was lucky I had another device with the same power adapter. I plugged in the new power adapter, and the modem was silent. The light was now a constant amber instead of cycling with the other colors. Ultimately, it gave me a useable IP address, and I was able to get my internet back. 

Hopefully this will be helpful to the next person with the same problem who searches these posts only to come up with reply after reply of “talk to customer/technical support.” Maybe you can cut to the chase faster