Is this not maybe a Google issue and not relate to the mirror module?
The only thing that i find is that in the Google Home app its asking for a Device Name. In the project section there is only a Project Name, Project ID and Project number. I have tried all 3 but no luck yet.
I used this feature for a shopping when it was still working. Asking Jarvis to add an item to my shopping list and then at the shops reading it off my phone and clearing the items as i go along