Loss of external monitor display
I use an external monitor to my MacBook.
Until yesterday, whenever I closed my MacBook, the external monitor continued to display my MacBook screen. Great.
However, this morning this has stopped working. When I close my MacBook, the external monitor goes dark and reports no input. I have tried re-starting and re-connecting. But no luck.
Any suggestions?
MacBook Pro 15", OS X 10.11