Space Bar issue with Final Cut Pro

That's strange. Almost like it's an Accessibility option. I searched but couldn't find how to get an enclosing rectangle as you've shown. As Tom asks, please rerun and post a new Etrecheck report.

Have you mapped the spacebar in your FCP keyboard settings? You said you installed a new macOS which I think should get rid of the old FCP prefs, but that's an easy thing to try again. Hold command and option while launching FCP and choose Delete Preferences. It will open the default Untitled library. Re-open the library you were working on and see if there's any difference.

Double check your Accessibility preferences to make sure that Full Keyboard Access is turned OFF.

Is Enable Full Keyboard Access unchecked?

Does the spacebar work for QuickLook in the Finder and to start and stop video in the QuickTime player?

Obviously, space bar to play/pause should work, and it does.

We need to try and find out why it is not working for you.

Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

Oh no! You've got CleanMyMac installed. This is generally considered malware around here. I'm sure Luis will chime in with his thoughts on the matter. You should completely uninstall it and then reinstall FCP. It's possible it's damaged your system enough that only a wipe and fresh install will fix it.

Plus you've got many anti-virus packages installed. I think the recommendation is to use just Apple and Malwarebytes that's run on demand, not continuously.

Also looks like you've been upgrading in place for many years since there's a Silverlight plugin which was deprecated many years ago. The fresh install would be a good idea for this too.

And finally, you have Chrome and it's terrible keystone daemons running. See https://chromeisbad.com for instructions on how to completely remove Chrome and the keystone software. Reinstalling FCP after removing these is required.

CMM is apparently very aggressive at removing files it considers unnecessary, but it appears these files are required by FCP. It's done damage to many people's FCP machines that the experts around here (not me) jokingly refer to it as malware.

I've heard that Edge and Brave are browsers that use the same rendering engine as Chrome but do not install the damaging keystone daemons. Be sure to follow the instructions at https://chromeisbad.com to completely remove all traces.

Another thing to try is to reset FCP preferences. Hold command and option while launching and choose Delete Preferences... FCP will open the default Untitled library. Open the library you were working on, set the preferences back to the way you like them and see if the spacebar issue has been fixed.

Report back with your progress and we can further diagnose if you're still having problems.

With the image file selected press the spacebar. What happens?

QuickLook isn't working then. Could you run another ErtreCheck report?

+1