I had the same issue, and finally downloaded the 8801 form and instructions from irs.gov, and completed the form manually to obtain the value from line 26 to be entered, which was zero in my case.
What I have learned in completing the forms and searching other responses on this site is that having an AMT credit is pretty rare unless you have stock options that are exercised in a different year than the year in which you sell that stock.
The irs instructions stop you at a certain point if the results are zero, and say not to complete or file the 8801 form, so this is perhaps why TurboTax does not have this information to carry over from prior years. However, I think this is a feature that should be included in the software, as all the data to make the calculations are already in there. Normally, I am a big fan of TurboTax, but I believe this is a flaw in an otherwise great program.
Good luck.
