New Phone Opening Issues

[LuluFrance]

Hi,

recently received Pine64 Beta.  Went through the quick start guide which was fine until I got to this issue:

• If the phone is plugged on charge it works perfectly, the screen is visible and functional.
  
• But, if the phone - even if fully charged - is not plugged in, the screen fades to black in about less than second.  Touch the screen it opens, but it's barely enough time to choose either a number for the pin code or to tap an app icon.  It's functional but it so fast as disappearing, that the area of the screen being tapped is 'hit and miss'.  If that makes sense.
  

I've checked the battery is in correct, and I've done a reset in hopes it was a glitch, but still happening.  Simply put - can't see the screen for more than a blink of an eye.  I've not put in a sim card nor changed the operating system since I can't really see the screen and the options to start using the phone.

Any help appreciated

thanks
Lulu