If you experience same issue, you can follow below:
1. Remove any sim card in your phone.
2. Press power button and volume down till it shows Feedback screen. Just press Home, and it will show home screen. Try this for a few times.
3. You can now try to go to Settings > Devices > About > Reset your phone. This will delete everything in your phone, which I assume it should be OK as you already run beta software.
There is also other instruction on internet, which I have not tried:
- Power the device off
- Press the power key once, device will vibrate
- Immediately press and hold the Volume Down key
- Exclamation point will appear, release Volume Down key
- Press these buttons one at a time in this order: Volume Up, Volume Down, Power, Volume Down
- Device should vibrate, reboot, show the Nokia flash screen, and then go to the spinning gears install screen.