Microsoft work account doesnt send push notifications for sign ins to Authenticator app

 Push notifications suddenly stopped working for me. Here is how I fixed it:

1. If you go to My Sign-Ins (microsoft.com), you can see all the ways in which you can sign in to your microsoft account.
2. In my case, "Microsoft Authenticator" was in the list, but on my phone within the authenticator app, my account was grayed out.
3. I deleted the "Microsoft Authenticator" item from the list and then added back again. The website prompts you through a couple of dialogs and then finally provides you a QR code to use against the authenticator app. Once I did this, the account was no longer grayed out.
4. The final step was to mark the Authenticator app as the default sign in method on the website.

That fixed my problem.

For more info: Passwordless sign-in with the Microsoft Authenticator app - Azure Active Directory | Microsoft Docs