unable to install plugin

– This typically means WordPress trying to connect to the update server in the background, but couldn’t. This could be due to a simple internet connection issue, or may be the server is offline. This connectivity issue, which usually resolves itself after a while.
– If not, try contacting your internet/hosting provider.
– Also, review this tutorial: http://www.wpbeginner.com/wp-tutorials/how-to-fix-secure-connection-error-in-wordpress/