Gridview thumbnails not working

こちらでも同じ事を困っています

Hi Hiroki, 

Welcome to the Box Community, I'm happy to help!

This would be something our Product Support team would like to investigate with you and may require specific account information. 

I've gone ahead and created a ticket for you so that an agent can work directly with you on looking into this. 

Kindly check your email for details and updates.

Regards,

I'm also having the exact same issue with box.com, no thumbnails for PDFs are loading at all. I've tried several browsers and a couple of different devices/platforms. It seems like thumbnails are just not being requested for the web version, I don't see any requests failing. thumb_123.jpg files are loaded in the network requests for images, but not for PDFs. There are no requests being made for thumbnails for PDF files. Thumbnails work fine on iOS app.