Do you have separate ad IDs for banner and interstitial?
Your impressions aren’t enough either.
I suggest you give it few days to get decent metrics, enough to judge the network’s performance.
Maybe some 60k spanning between minimum 3-4 days would be enough to judge performance.
Seems like I was using a Legacy ID, I created Separate banner one months back, but was using Legacy ID for Banner and Interstitials.
Atleast now I can monitor each one. Maybe Clicks and Earnings might increase using the new Interstitial ID.