How to fix a frozen Onyx Boox

1.please press the power button for 8-10 seconds to reset your device.

2.Or you can try to restore the factory default settings as following steps:
Switch off the device firstly, and then long press “back + power” buttons at the same time , enter into recovery mode. Now choose “wipe data factory reset – yes, delete all user data – reboot” to restore factory default. This will delete the personal data (such as reading history, applications, some personal setting) but won’t delete files in storage.