Try these steps to troubleshoot Microsoft Authenticator Not Sending Verification Codes to iPhones.

* Check if the Microsoft Authenticator app is up to date. You can update the app from the app store on your mobile device. (Open the App Store, Tap your profile icon at the top of the screen, Scroll to see pending updates and release notes, Tap Update next to an app to update only that app.)

* In your iOS device settings please make sure that battery optimization is turned off for Microsoft Authenticator App and it is allowed to run in background. (Go to Settings > Battery > Battery Health & Charging and turn off Optimized Battery Charging.)

* Ensure that your mobile device is connected to the internet and has a stable network connection. The Microsoft Authenticator app requires an internet connection to send verification codes.

* Check if the app has the necessary permissions to send notifications. On your mobile device, go to Settings > Apps > Microsoft Authenticator > Permissions, and ensure that the app has permission to send notifications.

* You can also try restarting both your mobile device and PC, and then attempt to log in again.

* Make sure Airplane mode is off.

* If using cellular, try switching to Wi-Fi and vice-versa.

* If the VPN is active during the issue, try deactivating the VPN to see if the issue persists.

* Make sure the device requires a PIN or biometric to unlock (lock screen). Try to re-enable faceID or fingerprint in the device settings and restart the device.

* Some errors are intermittent. If you ran into a problem previously, retry your sign-in to see if the problem still occurs.

* If passwordless sign-in doesn't work, try signing in with a username and password and use a time-based one-time password (TOTP) in Authenticator for two-factor authentication as a temporary workaround.

* Make sure notifications work.

* Check if push notifications are turned on for the device and Authenticator. Tap Settings > Notification Settings and make sure Show notifications is turned on.

* Check if push notifications are turned on for the device. On an Android device, tap Settings > Notifications > App settings and make sure Authenticator is turned on.

* If you get an expired notification, make sure the device's Date & time are correct. Tap Settings > System > Date and time and make sure Automatic time and date and Automatic time zone are turned on.

* If you don't see push notifications in the list session in Authenticator, you can swipe down in the list view to check for pending authentications. You can sign in by using the pending authentication as a workaround.