The Mashshare Pageview add-on is using a custom ajax url which is faster than regular the /wp-admin/ajax.php
The path to it is yourwebsite.com/?ajaxmash=mashpvsetviews&id=2 (id depends on the id of the post which is counted)
If you are using any web accelerator like Varnish make that you exclude this path from caching.
Make also sure that varnish is purging its cache after an amount of time (a few hours), otherwise the page views are never counting up.
