If you get an error 500 and the website is not opening check if you are using the plugin WP Super Cache version 1.5.10 or lower.
This version is not compatible with WP Super Cache so the caching plugin must be disabled on the staging site.
Do do that afterwards you need to rename the folder
to anything else. Use a FTP program of your choice for that.
Alternatively you can
- Create a new staging site
- Exclude the WP Super Cache Plugin
The staging site should be working now.
This issue is solved in WP Super Cache 1.5.10 and higher