Joomla is a heterogeneous environment: there are a large number of extensions published by different developers. While sigplus does its best to be generally compatible with a wide range of them, there is always a slight risk that any two out of the thousands of published extensions just do not work well together. I think this might explain why the extension does not work in IE for you while the demo site displays perfectly. (A word of notice: sigplus is not compatible with ancient versions of browsers that had been obsoleted even before sigplus was published in the JED.) If you run into a similar support issue or encounter a bug, please contact the developer directly about it. The review system is one-way: it allows only a single reply to each review and does not allow contacting you for specifics. As such, it is far from a practical way of asking for help.