GameManager script corrupted, old versions no longer work

My scene recently stopped working and I believe my GameManager script has an issue. The objects do not appear and the text has been replaced with 'Hello World', all of which are controlled by the GameManager. No error messages appear. Even when I revert back to an older version of the script that I know worked, I still have the same issue. Is there some setting that may have been changed that may have caused this?

Thank you!!