In order for your device to be authenticated, your date/time needs to be set to automatic and/or be accurate within +/- 1 minute. This will be fixed in the next update; if you have not updated your device to the latest version of our app, please do so.
In the meantime, check your device's Settings, under the "Date and time" section (or similarly named section). If you have a setting for Automatic date and/or time, enable this setting.
Alternately, verify that your device's date and time is accurate within a few seconds to another source (such as http://time.gov/). If it is not, please adjust your time and try restarting the app.
Thank you for your patience.