Q: My system preferences-display doesn't recognise my additional monitor, although it did so before.  I have re-booted etc.  Any ideas?

Hi,

I have an external monitor to use with my Macbook Pro (Dell U241M). In system preferences, this monitor shows under 'Colour' but not 'Displays'. It was working until a few weeks ago when someone else used the monitor for thier Macbook. I do have the correct thunderbolt cables/connectors etc.

I have tried rebooting both the Mac and the monitor without success.

Help would be appreciated.

Cheers,

Ken