Twitop already mentioned it (tnx for the head’s up on this post), but just so you hear it from us too (the developers) :
We clearly state that this plugin uses a parser that is normally part of PHP. In certain server configuration settings this parser may be turned off or may not be available. We do not have the resources to go in to everyone’s server and check settings. You can install the free version right here at www.ads-software.com and see if things work before you commit to a (dirt cheap) commercial version.
Either way, if you really cannot get it to work and accidentally got the commercial version we’ll refund you as was stated above. We’re not getting rich on these plugins, we’re just trying to get paid a little bit to keep our servers running.