Hello. My name is***** to JustAnswer. I'm reviewing your question now, and will post back with your reply momentarily.
Let me explain how this will work for you. You went thru an automated system, then got sent to a human.
I will ask you questions, you reply and we come up with several techniques (if needed) to troubleshoot your
error. But, please keep in mind, not all hardware/software can be fixed. Especially grey screens like you have,
but if we work together, we can try as much as possible to get it going again.
Try this for me first?
Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
Turn on your Mac.
Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
Hold these keys until the computer restarts and you hear the startup sound for a second time.
Release the keys.
Let me know what happens?