I continue to have this same problem. I have been using the Nest App for years without error, then I started getting notification that the Location is not enabled in the Nest App (for use by home /away assist). It is on. I have uninstalled the app and re-installed (with a customer service specialist) but I still get this warning.
@gillgeorgew, thanks for posting and for being a step ahead of us. A few things: What is the make and model of the mobile phone that you are using for your Nest app? Which Nest devices? Try using another mobile phone to further isolate the issue.
Looking forward for your response.