Q: cap locks key won't work

Try going to System Preferences - Keyboard - Modifier Keys... and make sure you have Caps Lock enabled.

Have you tried disabling that option and then enabling it again? Sometimes this helps.

Also, take a look at these articles, maybe they will help you:

One or more keys on the keyboard do not respond - Apple Support

Keyboard Caps Lock modified to reduce accidental activation - Apple Support

I'm going to ask you quite a silly question: are you sure that the Caps Lock key has no water damage?

What keyboard are you using?

This is the Mac Pro desktop forum.

I suspect a problem with the keyboard.. Do you have a USB KB to test with?

In this case, you may try going to System Preferences - Keyboard - Shortcuts and clicking Restore Defaults.

After that, to System Preferences - Keyboard - Modifier Keys... and Restore Defaults once again.

Please note that this will change all the keyboard settings to default, so if you previously had some custom-made shortcuts, you will lose them.

I requested this discussion be moved here:

MacBook Pro

No action on your part is required

I have had the same issue but did this and it works

Go to System Prefs / Keyboard / Modifier Keys.

Now change the Control Key oprion to show Caps Lock. (Don't change the others)

Don't ask me how it works biut it does.

I should also add that my screen shot now works too (Cmd + Shift + 3) as a result of this change.

Mysterious