iTunes connect - app sales not showing 2 people told me (in the last 24 hours) that they bought an app I sent to App Store, but neither App Analytics nor Sales and Trends in iTunes Connect show a thing, they show there isn't any sale and no analytics at all.

How can I see the information of the app correctly? Why is this happening?
iTunesConnect stats are not real-time.  It usually takes 24 hours, sometimes longer depending on where the sale took place, time of day, etc., for app sales to be displayed.  If it's been more than 48 hours since the sale and you still don't see it in iTC, contact Apple's developer support.

For analytics, the user has to explicitly tell Apple that they want to share analytic data and logs with both Apple and the developer.  That question is usually only asked once during the initial iOS setup on that device.  Did both those users indicate they're willing to share this data?  If not, you won't see it.  The user can change their selection in Settings but it's a global setting and not for each different app/developer.