It may be due to an implementation issue.
If you observe a low viewability rate, it is possible that it has not been implemented correctly on your advertising setups.
The mobile sticky bottom (or sticky footer) ad format generally performs well in the AMP environment, having around 90%+ viewability rate.
Please, reach out so that we can fix this issue together.
Learn more about viewability rate, one of the top advertising metrics to follow.
Understand how we analyze the viewability on our publishers dashboard by watching our video tutorial.