I've used Windy for a long time now.
It seems the Radar and Satellite overlay no longer pulls radar data from JMA (Japan Meteorological Agency). This is no matter what zoom level I use. It always shows "loading" dots, and Japan has a grid of dots over it. Neighboring Korea and China have radar data displayed. (NMC).
OS : Android
App ver: 28.1.1
Build date: 2021-02-16
I don't know how to enter a screenshot.. let me try.. link to the album is https://m.imgur.com/a/ELnvnu4 if they don't work.