On those 3 different files you mentioned, does this happen every time you try to print to PDF? Or sometimes it saves the PDF and sometimes it doesn't?

Does it happen for all three copies (Filing Copy, Client Copy, Preparer Copy)?

https://proconnect.intuit.com/community/help-articles/help/remove-and-reinstall-lacerte-and-dms-pdf-... may help

It happens on all 3 forms.

Still looking for a solution.

You are logged in on your computer as a certain user. That user, or the user group it belongs to, must have write access to the "C:\ProPDF\TY2020" folder. This is separate from the folder where your ProSeries installation is, typically "C:\ProWin20". 

While I could see that being an issue if I was on a network, the fact that this is a private computer with only one user that has run ProSeries for more than 5 years, I have not changed any access rights.

I welcome any further suggestions ASAP as I am beginning to stack up returns.

It may be user rights https://proconnect.intuit.com/community/manage-access/help/manage-users-for-proseries/00/4963

NOTE:

If you are the owner of the firm, manage your office, or are the only ProSeries user in your office, you must: complete the initial setup, and invite additional software users (if applicable).

Only user.  Setup as Admin.  Verified access.
What else can be done?

Just for a test, change the location where PDF files are saved. Pick a folder (create it first) under C:\users\yourname, let's call it C:\users\rick\TY2020PDFFiles. See if that makes a difference. 

This is how you make this change:

This was a good idea.  It didn't work, but a good thought.
I was on the telephone with the Intuit people and they had remoted into my computer and I had them stumped.  I had high hopes when the tech put me on hold and said he would discuss with a manager.  Hopes right up until he disconnected.

Open to more ideas.

Can you actually print to the printer? Or that doesn't work either?

Turn off your antivirus just to let ProSeries create one PDF and see is the PDF is there? Then turn the antivirus back on.