Diagnostics for my 1120 included a message that the penalty form 2220 could not be calculated due to the interest rate being unknown. It advised that I should either suppress the penalty or prepare it manually and attach. When I review the return I can see that the penalty did indeed calculate and appears on the front page of the 1120. A chat with support got me nowhere and I was advised to simply suppress the penalty. The software should do a better job. I lost an hour today on this ridiculous situation.