Apple - CMD + space not working in the first try
i saw this on a user's machine lately. it was acting very strangely with a couple command keys.
the solution here was to go to keyboard preference pane and clear out all shortcuts and restore defaults for each section. it seems an app this user installed was grabbing the key-combo for its own purposes, and once removing the customizing it worked well.
it might be this simple in your case.
Per this blog post, if you are connected to an external monitor(s) changing the desktop resolution to something else and back worked for me. Spotlight was working the whole time just off the screensomewhere:
∙ Step 1:
Open System Preferences/Keyboard and select Keyboard Shortcuts
Click Spotlight on the left. Make sure the shortcuts are correct. If not, click: Restore Defaults.
∙ Step 2:
How to reset NVRAM or PRAM on Mac:
Apple Support: https://support.apple.com/ht204063
YouTube tutorial: https://www.youtube.com/watch?v=MPzu7n_q6ag
Note: For me it solved the problem.