For some reason, whenever you update a theme option and click "save", then it redirects you to a 404 error and no information is saved.
1. Go to Settings > Permalinks > Set to default /?p=123
2. If new error will appear
"Forbidden You don't have permission to access /wp-admin/options.php on this server. Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."
3. Need to contact your hosting customer support with request, check mod_security Specific rule ID 340007 must be disabled on your server.