When I try to edit a post, the program hangs with the working icon spinning.
Chrome Developer Tools reports:
ajax.js:561 Uncaught ReferenceError: tinyMCE is not defined
at Object.<anonymous> (ajax.js:561)
at i (jquery.js:2)
at Object.fireWith [as resolveWith] (jquery.js:2)
at y (jquery.js:4)
at XMLHttpRequest.c (jquery.js:4)
(anonymous) @ ajax.js:561
i @ jquery.js:2
fireWith @ jquery.js:2
y @ jquery.js:4
c @ jquery.js:4
XMLHttpRequest.send (async)
send @ jquery.js:4
ajax @ jquery.js:4
(anonymous) @ ajax.js:547
dispatch @ jquery.js:3
r.handle @ jquery.js:3
I think you have some JS optimizer plugin which minify JS files and damages. Please deactivate all Optimizer and Minifier plugins, delete all cache and test it again.
Also this maybe caused by JS error of other plugins or the active theme, please leave your website URL to allow us debug all JS errors.
Your theme is incomplete. It doesn't have footer hook for plugins to load JS files.
footer.php template file of all themes must contain <?php wp_footer(); ?> template function before </body></html> closing tags. I think it doesn't exist in your theme. I'd recommend to change this theme and test it again. Also make sure all cache plugins are disabled when you check any problem.