The channel was only just added
Outliers are found when a channel syncs. Give it until the next sync. See How often channels sync.
Not enough history
A baseline needs at least 5 videos earlier videos. Before that, YTNiches can't tell what's normal for the channel, so it doesn't call anything an outlier.
Nothing has broken out
Plenty of channels are steady. If no video has reached 3× the channel's baseline, there's no outlier to show. That's a finding too: the channel is consistent, not explosive.
It's outside your date range
Your outliers shows videos published in the last month by default. Switch the filter to 90 days or All time to see older ones. Trending also only covers outliers found in the last 7 days.