This article covers the most common reasons for discrepancies between data you see on YouTube and the results in your Supermetrics reports.
Data delays
The API may be up to 2 days behind on some video insights, so checking very current values (like today or yesterday) may not align with the Analytics UI reporting in YouTube.
Monetization data
You can only pull monetization data for channels that have monetization enabled on YouTube. Make sure you're eligible for YouTube's partner program and that you've completed all the steps to turn on monetization for your YouTube channel to access monetization metrics.
If you try to pull monetization data for a channel for which monetization isn't turned on, you'll get an error.