When e-filing a Colorado individual return extension request, I receive an error indicating that "The extension does not meet the conditions for electronic filing.  Form DR 0158-I is not active.  Check the freeze box to activate."

On the Form DR158-I worksheet, I DO have the freeze box checked, and the return passes the error validation.  Anyone have an idea as to why I would still be receiving this error?

Also, income tax expected to be owed is $0.00 because of a 2020 over-payment carryover.