Some of Applovin’s advertisers pay on a CPI (cost per install) basis, which means Applovin and you, as the publisher, only get paid when a click produces an install. Sometimes this takes a few days depending on the number of clicks you have and the tracking platforms our advertisers use to report installs back to us.
In addition, after enough traffic is served, AppLovin ad serving algorithm learn which campaigns work best on your placement and eCPM is expected to improve.