Might your router be one supplied by your internet provider? If so, your problem may have been caused by a recent update to your router. This has been reported lately with equipment from Xfinity and Cox, but there may be others.
Affected users report the router configuration needs to be switched from g/n security back to b/g/n. If you don't have access to your router's control panel you may have to have your internet provider do it for you.
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