Sunday
Why is the login failing with the newest iOS Nest app? Credentials are working perfectly fine via a browser on my phone. Work fine via browser on MBP. iOS app is broken. I have not and will not migrate from Nest credentials to Google, as I have first generation equipment (thermostats, cameras & smoke detectors).
Answered! Go to the Recommended Answer.
Sunday
So, perhaps I fixed this myself. When I first encountered issues yesterday, I deleted the app from my phone and reinstalled. Things seemed to work, but then failure again. I also went through the process of turning on 2FA. That also failed. Just now, I turned off 2FA, deleted the app, rebooted the phone, reinstalled the app. Now it appears to be working. Thanks to myself.
Sunday
So, perhaps I fixed this myself. When I first encountered issues yesterday, I deleted the app from my phone and reinstalled. Things seemed to work, but then failure again. I also went through the process of turning on 2FA. That also failed. Just now, I turned off 2FA, deleted the app, rebooted the phone, reinstalled the app. Now it appears to be working. Thanks to myself.