And there is no one single answer. There are buttons to push to switch on the external but I didn't read where you tried that. Also, there is a lot more posts where folk write "Windows doesn't recognize" and the brutal truth is that Windows doesn't recognize much automatically.
It may seem odd but decades later we are not much better off when it comes to things just working.
Have New Dell Inspiron N5010 laptop with windows 7. It was set up originally to use my Acer AL2416W monitor which is connected to my Dell Inspiron Desktop. After a few days, the external monitor went black and stays in hybernating mode. I have a netgear wireless router. How can I get the external monitor recognized again to use with the laptop? Thanks for any help.