MacOS Sierra Display Problem - Can't Detect Projector | How to fix the problem?

In my work, I often do presentations and connect my MacBook Air (Mid 2013) to a projector.  I bought a VGA adaptor from Apple Store and it works perfectly until last Saturday when I did a Canadian Immigration Consultancy presentation at Lipa City.  Suddenly, the projector can't be detected and my monitor went black.

I have 2 VGA adaptors and changing it didn't solve the problem.  Restarting my Mac did not help either. I checked the Display settings and to my surprise, there was no Display Arrangement Tab! Panic followed.

A colleague, fortunately, brought his laptop. I tried connecting the projector to the laptop and worked fine.  Thus, it's confirmed that the problem was with my Mac.  I had to do convert my Keynote presentation to a Powerpoint format and let go of those awesome animations. But that's ok.

I suspected that the problem was caused by the recent update in the OS.  I remember updating to macOS Sierra Version 10.12.5.  I asked my friend Google and apparently, it is a problem experienced by many users.  Unfortunately, there seems no solution until now.  Well, some users made it work after restarting their Mac with the projector connected.  It did not work for me.

There was also a suggestion to buy a new VGA Adapter compatible with the new OS. Another suggestion is that VGA is no longer supported by the new OS and that external displays should be connected using HDMI.  I have not tried these suggestions yet.

From the Apple Support Forums, their standard answer is to read Get help with video issues on external displays connected to your Mac.  But it does not really address the problem.

I will be visiting Apple Store one of these days to fix this problem.