Here the most common reasons:

You are looking in a period in which you haven't installed Reaktion. 

It could be because you haven't installed Reaktion during the period you're reviewing. Our server-side tracking initiates once you've integrated your ecommerce platform and marketing channel. If you've recently installed Reaktion, please try selecting a date range from the past few days.

Your Google Ads account hasn't accepted Customer Data Terms

A must-do for our Google Ads serverside tracking to be working. Please see our guide here.

You are not using Google Tag Manager yet

Please see our guide to start using GTM to improve tracking accuracy