Dear @Ragavendra Ramesh,
Thank you for reaching out to Microsoft Q&A forum. We are happy to assist you.
To ensure everything is set up correctly, please follow the steps below to register the Microsoft Authenticator app on your mobile device:
Sign in to the account you want to add to the Authenticator app by visiting https://office.com.
On the Start by getting the app page, click Next.

Stay on the Set up your account page while you configure the Microsoft Authenticator app on your mobile device.

Open the Microsoft Authenticator app on your phone. If prompted, allow notifications.
Tap the Customize and control icon (three dots in the upper-right corner), then select Add account > Work or school account.
Go back to the Set up your account page on your computer and click Next. You’ll see a QR code.
Use the Authenticator app to scan the QR code displayed on your computer screen.

After scanning, click Next on your computer. A test notification will be sent to your mobile device.
Approve the notification in the Authenticator app, then click Next on your computer. Your security info will now default to using the Microsoft Authenticator app for two-step verification and password resets.
From this point forward, your authentication method will be registered and ready to use.
Once you've completed these steps, could you please confirm whether you saw a prompt to register the Authenticator app?
Also, just to be sure, may I ask if you downloaded the correct Microsoft Authenticator app published by Microsoft Corporation? The app looks like this on apps store:

This information will help us provide more tailored and effective support.
If you need any further assistance or clarification, feel free to reach out. We're here to help. Thank you very much for your understanding and your cooperation.
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