My roku express can see my wi-fi and reports the wi-fi connection is Excellent. However, it is very spotty in actually connecting to the "excellent" wi-fi and periodically says it is not connected at all. Restarting the wi-fi and the roku do not seem to fix it. Moving the roku position helps sometimes but other times nothing helps. The roku is only 2 years old so it's frustrating to be having such frequent issues with it, and even more frustrating that roku has decided my device is not eligible for agent support... Does anyone have any ideas?
Your Roku Express is a budget model that only supports the 2.4 GHz wifi band. It cannot even see the 5 GHz band employed by dual band routers.
Some equipment suppliers have sent updates to the 2.4 GHz band settings for their routers which affects some Roku models. If you receive this update it changes the router's wifi connection parameters for the 2.4 GHz wifi band from b/g/n to g/n. This has been reported for routers supplied by Comcast/xFinity, Cox, and AT&T, but there may be others.
Affected users report the Roku identifies the local network as available and rates the connection quality, but will not then connect to the internet, which sounds like the symptoms you're reporting. The fix is to switch the router configuration protocols from the g/n wifi set by the update back to b/g/n.
Thanks to forum user @AvsGunnar for providing the links below to instructions for reconfiguring router settings for the listed internet suppliers. If you can't do this yourself, you may need to contact your internet provider to make these changes for you: