Thank you George, that solved the issue.
I had entered the dates under 2.1 miscellaneous information, which in looking more closely is exclusively for short tax years. The majority of our fiscal year estate returns are short year so I am used to entering information there. Under page 1, box 5 entering the end month (05) automatically populates the dates on the return and I was able to successfully e-file.
You help is very much appreciated. Dan