You need the GD library installed. Turn on wordpress debugging. There is a link in the readme to the documentation and instructions on how to set it up. Did you even read the installation instructions here http://wordpress.org/plugins/flexible-captcha/installation/ or here http://www.jsterup.com/dev/wordpress/plugins/flexible-captcha/documentation?
I read it over and over — many times. I just never saw any mention of needing the GD Library or specifics on how to get it to work.
So you give it a 1 star rating because you cant understand how to use it and without asking for help? Well I guess maybe that’s why it isn’t working.
Help was asked for through your contact page a few weeks ago prior to me posting this. I received no response. So I assumed this was an unsupported plugin. And I rated it 1-star because I could not figure out how to make it work (the WP Rating system for 1-star is ‘poor’ and 2-star is ‘works’. Since it did not work, I used the 1-star rating). Again, I think the documentation needs some work. You are too close to the plugin and you are making way to many assumptions where as the plug-in installer has no prior background or knowledge of. I am sure the plug-in is great once you get it to work. Unlike many of the plug-ins on WP this one takes a lot of patience, guess-work and trial and error before getting it to work.
I never saw an email from you and have responded to the few emails I got for support over the past few weeks. You tried to make it do something it cant do. Then after it wouldn’t do what you wanted it to do, and wasn’t programmed to do, you rated it as doesn’t work.