Hi,
1. Did you set up the email account in the email account page marked as default?
2. Did you add email address of the approver in the Approval user setup?

3. Did you use Notification Setup in Approval user setup and can you share the screenshot too?
4. Check if the below highlighted part is present in your workflow?

if all the points mentioned above are covered and still you are unable to receive any notification then kindly share the screenshots for the following Approval user setup, Email accounts, Notification Setup, Workflow.
If my answer was helpful to you, please verify it so that other users know it worked. Thank you very much