I also have the problem described above.
"My Chihiros" was previously installed from the Apple App Store. After updating the app, I need to log in again. The app will not authenticate a login with any of the options. I also cannot "Sign up" with a new email address. When I attempt to try anything, I get "working on it" icon (the outline of a dragon that fills in red), then the error described above.
This happened after updating to version 2.7.80