I've spent several days troubleshooting issues for people who downloaded my free extensions. In every case, the issue was caused by their bad decisions and poor implementations.
Here's a tip to avoid wasting the time of someone who is, essentially, doing you a favor by giving you free software. Before you send email, or post to a forum, or write a bad review - do a reality check. Ask yourself the question - could it be something I did? When all of the reviews are good, and you can't make it work - chances are that you're doing something wrong.
A way you can check is to perform a clean install. A fresh installation with no additional software, just the core - and the extension. Follow the instructions. If it works, then you know it's your fault and not the developer or the software. If it doesn't work, then make your accusations (but be polite about it).