Theme Editor cannot save changes in style.css file

Whenever I make any changes in the ‘style.css’ file in my “child-theme” editor, and click to ‘update Change’, I get the following message:

“Something went wrong. Your change may not have been saved. Please try again. There is also a chance that you may need to manually fix and upload the file over http://FTP.”

This tarted happening almost two weeks ago – it was working alright until then.

Any help to fix it is greatly appreciated.

Thank you.

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