Hmmm. After trying most of the suggestions, I took hold of the screen by the right and left corners, and applied torque, gently. A couple of wiggles, and the screen came on.
That sounds like a loose internal connection. Laptops by their portable nature are subject to vibrations that might work a connector loose. Laptops typically have several ribbon connectors, such as one that connects the screen module to a video controller. If the problem persists, I would ask a repairman to open the laptop and reseat all the connections.
A credit card applied along the edge of the frame will pop out the frame. You can then see the connection.
How to video.
https://www.youtube.com/watch?v=4KvYc6pDPOQ