Try starting the Macbook in safe mode:
To start in Safe Mode, turn it on and immediately after you hear the startup sound, press and hold the Shift key.
Release the Shift key when you see the Apple logo appear on the screen.
Let me know if that works...
When you are logged in to the JustAnswer website, you can reply back to me on your question page.
What exactly are you seeing in the black box on the middle of the screen?
Could you attach a photo of what you are seeing?
Thanks for the photo.
This error message can happen if the memory modules inside the Macbook are faulty or not detected.
You will need to try removing the memory modules and firmly reinserting them again.
If that doesn't work, you may have a faulty memory module and you will need to try fitting a replacement one.
* Ensure you observe appropriate anti-static precautions when handling the memory modules to prevent damage to them *