If your ads are not showing, please make sure that:
1. User permission "View ads" have been set from Admin > Users > User Group Permissions for "Registered" and "Unregistered/Unconfirmed" user groups.
2. You are not using invalid criteria or impossible criteria combination. For example, using "Privileges and Status" in User Criteria with multiple options selected, that cannot validate (a user cannot be a guest and logged in at the same time).
All criteria is optional and unless you know what you do, you should not use it.
3. Your ads are inheriting the package settings (if using packages).
4. Your ad_ prefixed default XenForo templates have the original hook in place. If not, revert the templates back.