Pls ensure that you have at least PHP 5.5 installed on your server. You can contact your hosting regarding the same. The current recommended version for WordPress is atleast 5.6 and preferably PHP 7.1.
The latest version of the plugin is not compatible with older versions of PHP. Although we have an internal update which has fixed this issue, I highly recommend everyone upgrade to 5.6+. We have had only couple of reports of this happening so far and hence I assume the number of installations is really small.