I am trying to change CSS of my wordpress website. I am changing code under wp-admin/theme-editor.php. But whenever i click on upload file button, an error appears 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 FTP.
I thought this happened because of plugin, so i deactivate all the plugins and tried again. But problem was still there. Does any one know how to solve this problem?
I also installed Health Check & Troubleshooting to find the error. Here is snapshot of health check https://i.stack.imgur.com/3uwJg.png