It looks like the background illumination significantly overpowers the front lighting in the shot of the camera. With an incident meter I suggest:
A. With the back-illumination off, adjust the front illumination for correct exposure. Then switch off the front lights.
B. Switch on the back illumination only. With the diffuser of the meter close to and aimed at the back-illuminated translucent surface the subject rests on, adjust the backlight until you obtain the front/back light ratio you want.
If you set both front and back lights to the same meter reading, the backlit panel will likely look approximately medium gray in the final photo. You’ll probably have to experiment to get the lighting ratio satisfactory to achieve the effect you want.