We hae a Toshiba Satellite which has a cracked screen. We’ve gotten a VGA cord and attached it to the new monitor. The laptop recognizes that there’s an external monitor, but the monitor has a “Check Signal Cable” show only and is not showing us anything on our laptop screen. We tried changing the resolution on our computer but otherwise are meeting dead ends. Can you help?

My Apple MacBook screen is cracked, and I'm going to buy a new monitor to replace. I do not want to consider that the Apple store and they are installed so there is no way I can change the screen itself? The installation fee is really expensive.
Thank you.