I figured out how to fix this e-file diagnostic for Ref #32702 stating PDF Attachment #1: Sent to nonexistent Form 5471. You will need to go to the Form 5471 and action the following:

1. Click on the three lines next to where it says "New Tab".
2. Next to "NO." 1 under "FILER", type the taxpayer's full name and click on "Details".
3. Go to the bottom of the page and tick the "I reviewed Form 5471 for diagnostic with reference# 2055537".
4. Enter a "1" in the box for "1=delete this year".  This prevents the printing of Form 5471.

When you are ready to print your final tax return to provide to the taxpayer, check that the "General Info." filing instructions page shows the "PDF Attachments" under "Federal" for Form 5471 Other with the name of the file you uploaded (e.g., 2022 Form 5471 (E-File Attachment) .pdf. PDF).