While we cannot go in and edit your files for you, we can provide you methods to either troubleshoot why the Code Editor isn't working or provide alternatives to the Code Editor.
The Code Editor will likely only work on recent browsers. Please try accessing it via a different browser than the one you used before.
As for if the Code Editor still does not work, there are two alternative methods you can try:
1. try loading the file in the text editor instead. There won't be any fancy syntax highlighting or anything, but it should get the job done.
2. download the file, edit it in a text editor such as Notepad++ or wordpad (don't use notepad as it tends to occasionally mess up .php files, and especially do not use Word or another editor of that sort!), then re-upload it. You can either use the cPanel upload/download things or FTP to upload and download files.