Just did a quick experiment and it's working like a charm.  For the full-year resident state, ProConnect Tax automatically computes the credit for Sch 6, taking into account taxes paid to all other states, and produces the statement that shows how the credit is limited, all without user intervention.  It's as easy as it can be.

Did you enter anything on State & Local > Other State Tax Credit > IN Other State Tax Credit?

Normally, if there is any conflicting input or omission on the return that causes full-year resident state to not compute the credit, there should be a diagnostic.  Did you review the diagnostic messages to make sure there is nothing amiss?