In-Meeting notification not working for Personal accounts

Question

Good day,

We are having problems with sending out notifications to users as they join a meeting.

Using this example we are able to send out notifications to users in same and even different Tenants.

https://github.com/OfficeDev/Microsoft-Teams-Samples/blob/main/samples/meetings-notification/csharp/InMeetingNotifications/Bots/InMeetingNotificationsBot.cs

However, when a guest user with a microsoft account (no tenantId -so a personal account) is sent a notification it is never shown for them in the meeting stage.

According to the support documentation this should be supported for a guest or even unknown user as long as they are invited to a scheduled meeting.

https://learn.microsoft.com/en-us/microsoftteams/platform/apps-in-teams-meetings/in-meeting-notification-for-meeting?tabs=desktop#feature-compatibility-by-user-types

Who can assist with this? Or what would be an appropriate mechanism to send a message to such a user.