We need some additional information. You mention "Roku Ready" TVs, but there's no such thing. Any TV with an HDMI port will work with any Roku player (with the exception of some very early HDTVs from the '00s that don't support 720p or 1080p on the HDMI port). When you say "WiFi ready", I assume they are "smart" TVs that have built in apps and you don't use a Roku on those TVs.
What are the model numbers of your Rokus? Ignore the light on the front: what do you see on the TV screen when you select the Roku input? Is the home screen there, and you simply can't connect to the network? How are you powering your Roku players? Are they connected to a USB port on the TV or to a wall outlet with a power cube? Are all of them connected via WiFi, or do any have an Ethernet cable?
If everything looks "normal" on the home screen, but you can't get any app to work, that sounds like your WiFi router has changed the channel used for the WiFi radio to one that Roku can't use. Your other networked devices might work fine because they can use channels that Roku can't. Without knowing the model numbers of your Roku, and without knowing exactly what is and isn't working, we're simply guessing here.
Dan
Roku Community Streaming Expert
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