You need to go all the way through your Colorado interview to get the credit and answer two questions:
There two screens near the end of the Colorado interview that you have to pass through and make the correct answers to trigger the Colorado Sales Tax Refund:
1. "Qualifying for the Colorado state sales tax refund" (this is where the question about days incarcerated is)
2. "Qualifying for the Colorado sales tax refund" (where you have to indicate your filing date)
Once you have clicked on Yes on the second screen, the TABOR refund will be added.
Let this be a lesson for all TurboTax users, that when you start a section in TurboTax, that you finish it.