Are you using a router supplied by Xfinity, by any chance?
Your problem may have been caused by a recent update to many Xfinity-supplied routers:
Xfinity users report the router configuration needs to be switched back to b/g/n security. If you don't have access to your router settings, you may have to request Xfinity to do this for you.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
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