How can I encrypt my Lenovo P2 phone (Android 7.0)?

[LenovoP2]

Hi,

I am trying to encrypt my P2 (Android 7.0) phone but without success. When I select "Encrypt", the screen says it will encrypt, the green-outlined android image appears and then the phone restarts. But then nothing happens, not even an error message. It just behaves as normal.

I have tried all the following things (which I found suggested on other forums) but none solve the problem for me:

Made sure battery over 80%
Made sure phone was plugged into a wall charger
Turned off WiFi
Turned off Mobile Data
Killed all running apps, besides the encryption settings screen
Turned the phone to landscape mode
Removed SD card
Removed SIM

Can someone please help?