Microsoft Authenticator not sending push notifications

Question

Hi, I'm trying to help a user configure MS Authenticator with their personal iPhone (i.e. there's no MDM solution involved that might affect things in this case).

On their company laptop, we go through the normal process in a web browser: my account > security info > add method, choosing authenticator app and proceeding through the steps. When they scan the QR code, they receive an alert reading "error receiving push notifications. make sure that push notifications are enabled on the phone and verify you have network connectivity". The iPhone is up to date and (in settings) everything within the notifications panel for the authenticator app is enabled (i also checked local network access and location in case they might cause trouble but there is no mention of the app there).

We've tried reinstalling the app once without any luck. Any ideas?.. Thanks in advance