Getting Warning in General Setting re: Line 59

I got this warning in my general setting:

Warning: An unexpected error occurred. Something may be wrong with WordPress.org or this server’s configuration. If you continue to have problems, please try the support forums. (WordPress could not establish a secure connection to WordPress.org. Please contact your server administrator.) in /home/XXXX/waterbottlechallenge.com/wp-admin/includes/translation-install.php on line 59

Also all the default themes are gone and I cannot install new ones. The error in the Themes section is: ERROR: The theme directory “twentyfifteen” does not exist.

How to solve this?