Mouse clicks not working on MacBook Pro, with both track pad and USB mouse This evening the left mouse button on the track pad on my MacBook Pro stopped working.


Rebooted.  No change.
Zotted PRAM.  No change.
Reset SMC.  No change.
Connected USB wired mouse.  No change.


I've found various discussions of the trackpad mouse buttons not working, but many of the suggestions suggest using a physical wired mouse.  But right now it's ignoring both.  

Hardware:
Macbook Pro 1,2 (17" 2006)
External Mouse apple small roller ball middle button (Mighty mouse?)

Verified that the external mouse worked on another computer.

Verifed that the battery is not swelling.  Track mouse clicks.  Just doesn't do anything.

What do I need to check next?
Here is what worked for me.

I am on a MBP Retina 13" Late 2013 and macOS Sierra. The pointer started to have erratic movements and generated automatic clicks. Then this stopped but the left click would not work at all, even with an external mouse (only the right click of the mouse worked).

I tried everything (NVRAM reset,...) but nothing worked.

Then I found a post (here) linking it to an issue with an external monitor - I plugged the HDMi of the external screen I use from time to time, turned the monitor on and voila !, the left click worked again !

The post is 3 years old but he bug seems to be surviving...