I am not sure what is meant by US Radar down, but when I use the following link in Windows Chrome and Windows Brave browsers, I see the radar intensities but the base layer shows "No Data" data stamps across the entire US.
https://www.windy.com/-Radar-lightning-radar?radar,37.674,-122.094,7
If I zoom in, I get base layer data.

This is absolutely a wonderful weather app. I have everything I need from the one app!