I've been using Fotolia/Adobe Stock for years, and have never had an issue opening files. Twice today, though. I've run into files that can't be opened because they were not saved with "Create PDF Compatible File" option turned on. #278590899 and #278590877. I'm informed that they can be opened using Illustrator. Trouble is, I don't own Illustrator (I use Affinity Designer and Photoshop).
Many thanks for your reply. I totally agree - this is marketed as a stock photo service - NOT a stock photo service for those who own Illustrator. Going forward, I will be sure to always preview before licensing.