[GoodNotes 5] Why can't I import .goodnotes files, or a folder of them, from Google Drive via the Files app?

Due to an issue with the Files-Google Drive integration, .goodnotes files on Google Drive can become greyed-out in the Files app and thus not selectable for importing into GoodNotes. If you cannot import .goodnotes files from Google Drive, try one of the following workarounds to import your notes.

Workarounds 

Import one file at a time from Google Drive

1. Open the Google Drive app.
2. Tap the ... icon next to a .goodnotes file > Open in > Open in GoodNotes. 

Import a folder of .goodnotes files from Google Drive

If you've been using auto-backup with Google Drive with .goodnotes as the auto-backup format, you can take these steps to re-import that auto-backup folder:

1. Access your Google Drive from a computer.
2. Rename the auto-backup folder on Google Drive to something like "GoodNotes-old". This step prevents future duplicates.
3. Download that folder via Google Drive for Desktop. (Here is an article on how to install Google Drive for Desktop.) Do NOT download the folder directly from Google Drive as this will download a .zip file that GoodNotes can't read, and may result in error "GoodNotes4Converter.Document Reader.ReaderError".
4. Compress the downloaded folder into a .zip file on your computer.
5. Upload that .zip file to a cloud storage (or AirDrop it to your device if you're on a Mac), where you can access it later via the Files app.
6. Import the .zip file to GoodNotes. You should have back the same folder structure.
7. GoodNotes will upload the new files to your auto-backup folder.
8. Delete the "GoodNotes-old" folder from Google Drive to save space if needed.