Who is your ISP? Comcast/Xfinity?
They and other ISPs have been messing around with router settings on devices they manage. In some cases they've disabled the 2.4 GHz network, and with others, they've changed the settings from b/g/n to g/n. In both those cases, a Roku that only connects on a 2.4 GHz network won't be able to.
I'm not sure if all Roku TVs are dual band, meaning they support both 2.4 GHz and 5 GHz networks. If your supports 5 GHz, and you have a network broadcasting on 5 GHz, then none of what I'm saying applies to your situation.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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