I have a MBP that suddenly stopped detecting an external projector. I have used the same laptop with the same projector before. Right now when I boot the same laptop to the Windows partition it works fine with the projector, so I don't think it is a hardware problem. Any suggestions as to what to try? I have tried the "detect displays" trick and that doesn't seem to work.
Thanks all. Turns out it is indeed an adapter problem.
For the record, the broken adapter did work for connecting windows partition to the projector, and also for both mac and windows connecting to an external monitor.
And also, even when it works,
ioreg -l didn't list the projector's name in the output.