Could be the electronics and a new board isn't cheap or easy to come by. Mine pulled a fast one in embroidery. My reverse button can be flaky.
When you say boot up - do you mean the machine actually turning on or the screen coming on? Have you changed whatever you are plugging it into? Sometimes the power strips go bad. Do you have another cord or can you borrow one? If you mean turn on at all, could be the cord or power switch. If you mean the screen, that might be the board.
Do you have another dealer in the area who can diagnose electronic problems? Especially connections?