What if Nokia phone crashes and doesn't work? How to upgrade the system?

1. Full-touch hard grid method is: press and hold the function key+camera key+volume down+power on key 10 second while the word Nokia is displayed on the screen, and the grid will start automatically after the grid is completed. Let's start!

2. For the keyboard, press and hold the function key+No.3 key+* key+dial key+power on key in the same way as the touch screen.

If the above methods cannot be upgraded, you need to go to the local after-sales service center for professional testing.