I think you’re right and this could be a permissions related issue. First of all I wouldn’t recommend chanching all the WordPress directory permissions, only the wp-content directory and not to 777, instead permissions should be 755.
Probably you can’t change permissions on your FTP client because you’re not the owner of those files, more about that here Understanding Linux File Permissions.
You can try a couples of things:
- If your hosting provider has cPanel or a similar panel you may find a file manager there that is just like an FTP client and maybe there you can change the permissions.
- Or you could SSH into the server and set the permissions with this command:
chmod 755 wp-content
More about changing file permissions here: Changing File Permissions