Overview shortcode module not reporting "Unique visitors"

The shortcut for the overview module does not seem to be reporting the count of “Unique Visitors”. It just reports a hyphen for that field. All of the other fields are populated correctly. Is there something I am doing wrong? Here is my shortcode:

[wp-piwik module=”overview” title=”” period=”range” date=”2016-07-18,now”]

Thanks!

https://wordpress.org/plugins/wp-piwik/