Google Maps voice navigation problem

[scsiguru]

When using the Google app on my Iphone 6+ and enter the place I want to travel to the voice turn by turn works. If I go into the desktop version of Google Maps, create a custom map, and send either an email link or notification to my Iphone and and then launch that custom map the voice turn by turn notification doesn't work. Is there a setting or something else I need to change to get the voice navigation to work on the custom maps?

 

[C DM]

The whole navigation doesn't work, or there's simply no voice guidance?

 

[scsiguru]

The whole navigation doesn't work, or there's simply no voice guidance?

The navigation works when I click on the link or notification. It's just that the voice navigation does not work.