varnish-status: check isset( $headers['Server'] ) 
varnish-status: check isset( $headers['Server'] ) 

Love the new status page! Viewing it on local MAMP server I get :

( ! ) Notice: Undefined index: Server in .../wp-content/plugins/varnish-http-purge/varnish-status.php on line 242

Checking isset() fixes it as expected. Matched my fix to the other variables that you do check :)
Ipstenu/varnish-http-purge