Stick up outdoor camera night time issues

I have stick up battery outdoor cameras but I am having issues with one of them.
I use it to keep an eye on wild hedgehogs passing through but the shot is normally very dark.
But last night, randomly, with no input from me, the screen was absolutely perfect. It only lasted about an hour though and has reverted back to very dark.
Please can someone tell me how to set it up so I can have the clearer shot all the time.
Screen shot to show what I mean.
Thank you.

Hi @user73136. Are there any other lights installed around the Stick Up Cam? The night vision should automatically come on when the Stick Up Cam is recording events at night. However, external lighting around the Camera can prevent the night vision from coming on, as it would not be dark enough.