rgwhitaker
The b/g/n Wireless Mode is for the 2.4hz band of your network. This issue is primarily limited to cable ISP (like Comcast/Xfinity, Cox, and AT&T). I would actually call them back and make them make this change. (you will likely get another representative. Tell them you have security cameras or baby monitors that need legacy b mode "enabled" to work). Do not take "no" for an answer.
With the above out of the way, your Roku Streaming Stick is also 5ghz capable. (dual-band capable meaning your device can use both the 2.4hz and 5ghz bands of your network). It is possible that when the router reset after power restored, it may have selected an incompatible channel for Roku on the 5ghz band. Roku cannot use DFS channels 52-140. Roku can only see/use non-DFS channels 36-48 and 149-165. Try changing the Wireless Channels in the Xfinity app for this router to use one of the above channels. Do not use "Auto" setting. Preferably, I would try selecting one of the channels in the high band (149-165. also try not to use 165 as that may be reserved/overlap for military use in some areas).
This is why having the b/g/n enabled on the 2.4ghz is important. If for some reason you cannot connect to the 5ghz band (ie. router chooses a DFS channel on the 5ghz band), then the Roku device has the alternative option to connect to the 2.4 ghz band. As it stands now, you cannot connect to either band likely due to a router setting and an ill-informed Xfinity representative. They cannot tell you that you cannot enable legacy-b mode on the router.
Sometimes, you can keep restarting the router and it may select a non-DFS channel (if this is the issue), but kind of like playing the slots. Easier to make the change in the router itself.
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Finally, another method is to purchase your own router. You can use it in conjunction with the Xfinity router by placing the Xfinity router in a "Bridge Mode" (thereby making it a modem), and using your own router with whatever settings you want. Xfinity would have no control over your router or the settings you choose. You could also just use this new router (as long as compatible with Xfinity) by itself without the Xfinity router in Bridge Mode.
The list of Xfinity compatible routers is here for reference. https://www.xfinity.com/support/articles/list-of-approved-cable-modems
If you place the Xfinity router in Bridge Mode, then you can generally use any router as long as second in line so can stray from the list of "approved routers". The above list is meant generally for those wanting to just use one router.
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Feel free to post back after checking into the Wireless Settings on the 5ghz band or if you still need more help. Please include router model number as well.
