Not all user pageviews on your site convert into a video ad impression. In fact, the following things can happen:
the user viewing your site has an adblock extension installed
the bounce rate of your site could be very high, or the user's time on page is so low it doesn't allow the player to load
the Unit is inserted in a point on the page where it cannot convert (for example, it's positioned too low in the page)
in the case of a Content Unit, you have chosen an activation method on mouse-over or click.
Additionally, remember that not all requests sent by a Unit become Impressions, since our player only delivers advertisements that are relevant to your site's audience.
To improve the conversions on your site, follow our tips on optimizing your activity on Viralize.