Creating a bootable Sierra image on Catalina
The 2014 MacBook Pro should be able to download and run the Sierra Installer.


Current Version is: OS X el Capitan 10.11.6 What&#39;s Next?


The answer to that question is the process you can / should follow to download the installer and then run the create script.

What specific error message do you get following the process here?

You might need to post a screen shot of exactly what the terminal window shows in case you've got a syntax error we can spot. Also, the diskutil list command showing the USB drive you target might help.