Applies to some extensions.
If you see this error, you might need to set some custom permissions or fix your FTP details.
Please read the error carefully and find out which folder needs to be chmoded to 755.
In this case you'll need to fix permission on the engine or cache folder or check your FTP Settings from Global Configuration (Server tab).
If you don't know what CHMOD is or how to handle permissions, click here.
Please also check this link for more details.
If the above fails, you should change the permission to 777 but please read the note below.