Looks like your first post, Welcome to NLG!
Perhaps your little white button (Test/Diagnostic) switch is bad? Can you put a meter on its terminals and see if it is working? As you said, with the door open when you press the white button the screen should go to the Test and Setup screens. If you are not seeing this happen then maybe the white button switch is bad, or it is not connected or possibly something is going on with your mpu board. See if you can verify the white button switch is ok and its wires do go somewhere and are connected.
Might be good to check the power supply also, and its fuses, but with the display screen showing the "Call Attendant" message that makes me think the mpu board is running, which I believe would mean the power supply is ok.
Was this machine working ok at one time, then failed? What is background history on the machine, that will help us to narrow down possibilities.
And please post a photo of the machine, just so we can make sure it is a PE+, believe it or not there is sometimes confusion about this. We don't want to be making assumptions and find out later you have a similar but different model machine.
.....
Also, this thread might be better in the PE+ forum for better visibility, more likely to get advice?
A moderator moved it, thanks. -knagl