My app has been approved, but still the ads are not showing.

There can be multiple reasons for the ads not showing.
Generally, it is helpful to use the Error Occurred event(s) of the components and examine the error message to find the exact cause of Ads not working.
The error messages are usually self-explanatory, but if you want any help, feel free to open a new topic on the community.

Before posting a topic, please do take a moment to read How to ask a question topic to know how to ask questions that will receive replies quicker.