Google Nest Doorbell not ringing

My googlefu and forum searchfu have not provided any answers, so appealing to the STW hivemind......

I bought a Google Nest doorbell, so if someone comes to the door and i am in the office upstairs I get an audio notification on my phone (and the dog doesn't bark cos no door knocking).

But I can't for the life of me work out how to get the thing to give me a ring on the phone, i get soundless notifications that someone is at the door, but this is hopeless cos i miss them. I can talk to MrsEpic when she is at the door trialling, but no dingdong

I have the doorbell set up in GoogleHome, and notifications allowed etc, but it seems impossible to make it ring. 
Is there something obvious i am missing? 

TIA 
Simon