Image showing black

Hi, im still new in the field

So, my problem might be easy to answer

Im creating an apps that help in building evacuation during emergency by changing the exit signage to dynamic sign, thus help the evacuation faster

When i use it in my room, the image appear (image 1)

But, when i use it outside, the image appear black (image 2)

edit : i realized that it is not black screen, the image appear but very dark (image 3)

I think it is relate with the surrounding lighting problem

How can i make the image appear solid on screen?

Im using Unity Version 2019.4.0f1

Vuforia 9.3.3