First check if this form are supposed to send e-mail. If it should, try switching this off and try it then. If that works, you probably have the wrong smtp settings in the web.config. You can also switch on logging with log4net where this will be more visible.
Missing or wrong smtp settings is the normal reason at least so check on that first.
But I get the email alright. So far so good. But I don't come to the Thank you page. I won't redirect me to that page and just stays on the filled form.
I've done a very nice form and linked it to a very nice thank you page for the user to end up after clicking the button. However, the user never gets to the thank you page. I've used the basic page for the Thank you page (and also tried several other page types just to be sure) but when the user clicks, nothing happens and s/he stays on the filled in form page. Any idea how to get further? Someone who has encountered this?