Hi,
Are you seeing any errors in your log file at this point, as it looks like the actual editor isn’t being loaded (it’s a JS library)?
If you could check that using the steps outlined in the article at https://codex.ww.wp.xz.cn/Using_Your_Browser_to_Diagnose_JavaScript_Errors that would be fantastic, also any other errors that may be encountered in the code it self should show up in an error log on the server (personally I like using the example info from https://codex.ww.wp.xz.cn/Debugging_in_WordPress#Example_wp-config.php_for_Debugging for this as it creates a file in /wp-content/debug.log with all the output)
Thanks for your response! I found out what the problem was…me. I wasn’t paying attention and was actually clicking a backup file, not a CSS file. When I click to edit a CSS file, everything is fine. Thanks again!
Sweet, glad to hear you got it sorted out!
Out of curiosity, what kind of backup file was it, that might be something I should keep an eye out for an exclude from searches in the future.