Help!! When I try to open my app for authoring, I get the message Error Opening File - There was an error opening the file. I tried in Firefox, Chrome and Edge browsers. Each had the same result. I was up most of the night trying to fix a difficult issue, got my app working correctly, finally, and now at 5:18 am I can't open it any more. I have no idea what went wrong.
Here is some info that may help:

I am really needing to get this app back. Can anyone help?
Thanks!
jhn1