When you see no data in Radar weather layer, it generally means that the radar data provider is no longer able to disseminate this data due to an outage. So Windy cannot do anything until the provider fix it.
BTW there is no need to multiply here the posts about the same subject.
What do you mean by "stop the Timeline when I'm outside Windy" ?
For me the time slider, when used in autoplay mode, stops immediately when I leave Windy.
If it is not same for you, you can click the stop button at least.
Or do you mean something else?