Left click not working after pressing CMD key?

jack_condon wrote:

After a restart everything functions as normal. But as soon as I press the CMD key AT ALL, my left click (on trackpad or external mouse) turns into a right click. I can do CMD+Left Click to get a normal left click after this.

Uninstall any and all third party Antivirus, Cleaners, Optimizers, VPN, speeder uppers....

 To trouble shoot further you can:

 —Try a SafeBoot https://support.apple.com/en-us/HT201262

  Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache,  etc. 

   Login and test. Reboot  as normal and test as caches get rebuilt.

In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a  reboot will put it back to normal mode.

This will tell you if third party interference; extensions etc are not loaded in safe boot mode. 

 —Test issue in another user (or guest user) account  https://support.apple.com/en-us/HT204443

  This will tell you if it a universal issue or isolated to your user/admin account. 

jack_condon wrote:

I am using a mid-2012 Macbook Pro (I know it's old but it's done me well so far). After a reboot it works perfectly with no issues. But as soon as I press the CMD key even once, my left click function stops working. If i left click it right clicks - if i right click it right clicks. The only way to get around this is to hold down CMD and click, only then does it function as a proper left click. Really not sure how to fix this issue.

What does a Command Click do...?

Are you saying you are using an external mouse..?

Does the trackpad function as expected?

Control click opens a contextual menu— this I do know.