Sorry for the delay here but thanks for posting. I want to check on this further.
A few questions — were there recent changes made on your Nest devices, the mobile device that you're using to sign into your Nest app, or on your Nest account before this started happening? Are you using an old Nest account to login or do you have a migrated Google account? Also, have you tried checking your Nest app on other mobile devices or using a computer's browser if the devices are there?