Hi Micheal.
I'm playing the Blend command and got the same issue.
I did double check. There is no curves selected.

When I try to blend the edges there's always a 'calculation failed' message.

You can find a screenshot here:
https://drive.google.com/open?id=1GsUcRBW3-gkzWyCQ5AwgvcdAKdSa5igc

Do you have any idea on how to fix that?
Thank you very much