The Bio 2 bases displayed time/date on the time and date set on the phone/tablet the Bio 2 is connected to. Each time the device is reconnected with the Striiv app, time and date are updated. To reconnect the Bio 2, simply double tap the Bio 2 with the app open. If that doesn't do the trick, you'll need to force quit and restart the app, then double tap the Bio 2 with the app open.
If tapping the gear icon on the gray device banner at the top of the app home screen does not show device info, the Bio 2 will need to be factory reset in order to re-pair with the app:
Turn on the device and swipe to the left of the time/date and battery percentage screens to select Apps > swipe to the second Apps screen to select settings > swipe to the factory reset screen and tap the check mark to confirm.
Striiv.com/start and battery % will then appear, which signals your device is ready to be paired through the following process: https://www.striiv.com/pages/set-up-your-tracker