I found this:

Missing Document

"8453 Signature Document" must be present.

Proseries did provide the remedy of attaching a signed form 8453 EO, but I did not intend to use that form. I was able to file the electronic extension after I checked a few more boxes on the form 8868 worksheet information section that were not required in the past when filing extensions for non profit entities.  I do thank you for the reply none the less.

Sincerely

I discovered that I needed to check a few more boxes on the form 8868 information worksheet, and then I was able to successfully electronically file the form without the signed form 8453 EO attached.

Thanks for trying to asssit.

Sincerely

It's not a ProSeries code; it's an IRS code.

"Either you have an electronic funds withdrawal request and you’re missing signature information, or you need to remove payment information. This is because signature information is only required for returns with electronic funds withdrawal."