Hello,
Thank you for providing your user key and explaining your set-up.
There is not any activity on this key, is it possible you were signed into more than one Google account when you retrieved the key?
Also, just to confirm - are you working with a folder of documents that are on your Drive (not on a Team or Shared Drive)?
Can you try moving this folder to the top of your Drive ( not in any subfolders) and then while in a Chrome incognito window (important), try to toggle the trigger by opening Doc Appender, click through until you get to Step 4, then you should see a 'disable' button the bottom of the sidebar.
Click disable> refresh your form>open Doc Appender and go through the set-up again to try a test submission.
Hope that works for you.