I had the same issue beginning of this year ~ 02/2019 and wrote to Airtable.
For this problem i got no feedback that it is solved, but after ~1 month i tried again after logging out and in again on the desktop and it worked with all my files.
(I uplo...
Still an open Bug, i can confirm, for some of my pdf’s ~1% the preview picture will not be made/shown.
Sometimes i have had luck and reuploading them helps, but with some pdf’s reuploading also 10-20 times does not help. Always corrupt thumbnail. I c...