I had the same issue and called support, had the guy walk me through resetting up the device and everything seems to work fine now. Hope this helps.
Hey neighbors! If you have fully charged up your Doorbell or the battery for your Doorbell and the device will not power on, please ensure you have charged the device for at least 8 hours. From there, you can try resetting the device by pressing and holding the setup button for 30 seconds. In the event the device can still not boot up, try reconnecting it from the Device Health page, similar to how @TKW17 did when they called out support team!
If you still cannot set up the device or bring it online, please give our support team a call at one of the numbers available here. We're taking additional steps to protect our team and help reduce the spread of COVID-19. This has resulted in longer than normal wait times. If you are outside of the US, please read our response to COVID-19 here to see how to contact support.