Does not seem to work on multisite installations

Works great on single installations. On multisite, does not show. I tried just installing it and not activating it on whole network, activating it on a single site, and this does not work. I also tried activating on whole network and entering phone number in one site, and this does not work. Any ideas on how to get plugin working on multisite? Thank you for any suggestions.

http://wordpress.org/extend/plugins/call-now-button/