The default functionality of Captivate is to not allow failure if you're using remediation. After working on the problem for a while I have a solution on how to use a variable and advanced actions to allow remediation but also have a user fail the question after remediating.
You can read the full write-up on my site at this address, http://monkeylogic.us/blog/captivate-remediation-failure-part-1/
I'll be posting part 2 later that takes you through the steps of how to allow multiple attempts before remediating and then giving users one more additional attempt before marking the question failed.
Enjoy.