Unable to sign in – Microsoft Authenticator approval not received

My account uses Microsoft Authenticator for two-step verification. Previously, sign-in worked correctly: a PIN was sent to the Authenticator app, I approved it, and access was granted.

Later, I deleted the app. After reinstalling the app and adding the account again, sign-in still requires approval through Microsoft Authenticator, but no notification, PIN, or approval request appears in the app.

I know my correct username and password, but I am unable to complete verification because the Authenticator no longer receives or displays the sign-in request.