Wifi works perfectly but Roku still won't connect

WmTB, if no light comes on when you connect the power either the device is dead or the power source is dead.  If it uses a USB power adapter try one from a phone or tablet.

Non-4K Express models can only see and connect to the 2.4 KHz wifi band.  Your Streaming Sticks and Roku TVs can see and connect to both the 2.4 and 5 KHz bands.  So this may be a problem with reception of the 2.4 GHz wifi band.

There are several setting possibilities for your router's 2.4 KHz settings that may be the cause of your problem. And to make matters worse, some of them can be caused by recently-reported router updates. These have primarily been reported with routers supplied by internet providers (Comcast/xfinity, Cox, and ATT so far), but it's possible they could also occur with other internet providers or user-owned routers that have received similar updates.

• ROKU LOCATES NETWORK AND REPORTS NETWORK QUALITY BUT CANNOT CONNECT
  Some router updates have changed the router's connection settings on the 2.4 GHz wifi band from b/g/n to just g/n, causing Rokus connecting to the 2.4 GHz wifi band to lose their ability to connect to the network. The solution is to set the router's configuration back to using b/g/n.
   
• ROKU CANNOT FIND LOCAL WIFI NETWORK AT ALL
  A) Some recent router updates have turned off the router's use of the 2.4 GHz band. Some Roku models, notably Roku Express/Express+ (not the relatively new Express 4K/4K+ models 3940/3941) and Premiere/Premiere+ (model numbers above 4620), are lower end units with single band Wi-Fi radios that only support the 2.4 GHz band. They, and many other devices of all sorts that are 2.4 GHz only, can't even see the 5 GHz band, let alone connect to it. If you have 2.4 GHz only Roku model and a dual band router with both 2.4 and 5 GHz bands, be sure the router's 2.4 GHz band is turned on.
  
  B) In the 2.4 GHz WiFi band, all Rokus support channels 1-11, as are used in North America. If your router supports 2.4 GHz channels outside this range make sure your router is set to use a channel in this range and that you aren't using an auto setting that could select channels outside this range.
  
  C) Rokus with dual-band wifi radios can connect to the 5 GHz wifi band in two ranges of channel numbers, 36-48, and 149-165. If your router supports 5 GHz channels outside these two ranges make sure your router is set to use a channel with these ranges and that you aren't using an auto setting that could select channels outside these ranges.

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:

• Xfinity / Comcast → ( https://www.xfinity.com/support/articles/change-wifi-mode-admin-tool-xfinity-xfi ) with a walkthrough ( https://community.roku.com/t5/Network-Wireless-Wired-Connections/Error-014-30-stuck-for-three-days/m-p/749057#M21380)
  
  
• Cox → (https://www.cox.com/residential/support/managing-your-in-home-network-with-my-wifi.html)
  
  
• AT&T → (https://www.att.com/support/article/u-verse-high-speed-internet/KM1046172). You can select your appropriate router from the drop down menu.

If your problem was not caused by any of the above, often a restart of the router (even if other devices are still connecting) followed by a restart of the Roku will allow the connection to be reestablished. Depending on your Roku model and Roku version number you'll find the "System restart" option under either "Settings > System > Power" or "Settings > System", or if more convenient you can just remove the Roku's power for a few seconds and let it restart.

Hello nearbell

Welcome to the Roku Community!

If you are getting an error code or message, refer to this link for common Roku error codes and their recommended actions: How to connect your Roku streaming device to the internet using Wi-Fi or Ethernet 

Furthermore, please be advised that Roku Express is only compatible with wireless b/g/n networks on the 2.4 GHz spectrum. Ensure that your router is broadcasting a 2.4GHz Wi-Fi network for the device to connect to.

You can also try configuring your router and use wireless channels 1, 6, or 11 which are the preferred channels in North America. Each time you change the wireless channel, you will likely need to apply/save changes before you are prompted to restart the router.

Please keep us posted and we'll continue assisting you from there.

Regards,
Karla