I have installed caching plugin, now i cannot access my website. An error message of Application error 500 msg is appearing on both front end and back end. I deleted plugin from plugins directory but the problem is same.
This is not working. I entered right username and password, this message appears:
Failed to connect via FTP! Please check your username/password!
Should be fixed 
Side note: if you used your WordPress password as the FTP password, then it’ll echo wrong credentials 