First of all, make sure that you have had active campaigns (if you are an advertiser) or have served impressions (as a publisher) during the selected time period. Otherwise it will all be zero as seen below:
If you have selected a period for which there should be activity to report, or the statistics simply keep loading without any data, then make sure to disable ad blockers you may be using. Ad blockers may interfere with the statistics and prevent them from loading.
Similarly, we do not advise accessing the Ambire AdEx platform with Brave Browser, unless you specifically disable their shields for Ambire AdEx and allow trackers and ads for https://platform.adex.network/.