The zero impression ad groups penalty shows you paused ad groups which have not delivered an impression in over 13 months. If an ad group has been paused and not delivered an impression in over a year is not contributing to performance and should be removed from your account to help clean up your account. You can use the automation to automatically remove these.
If there are paused ad groups you would like to keep in your account when turning on this automation, apply the label "Squared:Paused" to the paused campaign or ad group and it will be ignored by Squared.io. However, once the campaign is activated, the label is automatically removed and is treated like any other campaign in the account