If an oCPM campaign has no impressions in the first few hours after moderation, there can be several things affecting the results: you could run out of budget, the banner or video may not work, or you may have set the desired CPI too low. In this case, we usually try running the campaign again with a higher price per action.
There may also be a situation where you set a specific CPI goal, but installations of the app are 2-3 times more expensive. For example, you set a CPI of 50 rubles (about $1 per install). At the campaign start, actual CPI may be at 100 rubles rate (about $2 per install), and then gradually decrease to 50 rubles over time. If the install price does not decrease in 2-3 days, we recommend removing this campaign. Probably, the creative did not "capture" your target audience, or you need to adjust the targeting.