I have used Roku for ten years. Today, it does not work. Is it down or something?
Everything on mine is working. What issues are you having and with what device. (Settings/System/About).
Assuming you tried the standard Roku restart and Router restart?
What do you mean? The vast majority of channels/apps would still work if Roku went out of business completely. The only thing you need Roku for is updates and "The Roku Channel". If you're having problems with multiple channels/apps restart all of your network equipment - gateway/modem/router.
When seeking help it's always a good idea to report your Roku model, model number, and Roku software version as shown via Settings > System > About. In many cases Roku will retain a model name when bringing out new versions, so the model number is important. Different models have different features and capabilities, and some things depend on the Roku version you are running. If we have this information to start with, you can get targeted suggestions more quickly.
There are some router setting issues that can prevent establishing Roku wifi connections. 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.
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:
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.