Changing project phase in Studio - users are not being notified?

Hello,

In the past few days when I changed phase to a project, the user assigned has not been notified.

The project had not been published after creation, I then published it and assigned users. Unfortunately they have not been notified that I passed the files on to them, and I am trying to repeat this task few times but still nothing's happened.

Could maybe anyone suggest what the issue might be?

Thank you!