For some reason, first my workstation and then my tablet stopped updating the wallpaper. First I thought it was my company that was avoiding the app to work properly but then I started noticing that the app itself is a mess:
It has two storage and formats for the wallpapers:
C:\Users\<username>\AppData\Local\Microsoft\BingDesktop\en-US\Apps\Wallpaper_5386c77076d04cf9a8b5d619b4cba48e\VersionIndependent\images
with a #####.jpg (single number) image format
&
C:\Users\<username>\AppData\Local\Microsoft\BingDesktop\themes
with a ####-##-##.jpg (date) image format.
I read here that deleting the themes folder it will get remade with the new images, and it worked. However those are not the files used by the Wallpaper app and deleting the images folder won't get the same result.
I have added Bing Desktop to the Firewall white list and the issue is still there. Any ideas?
Currently I'm using DisplayFusion to place the wallpaper manually because the company doesn't allow change the wallpapers (policies).
Note: I wrote to the DisplayFusion developers to suggest adding a feature to support Bing Wallpapers. They told me there was no API support to implement it but they will study this possibility (workaround) for the future: https://stackoverflow.com/questions/10639914/is-there-a-way-to-get-bings-photo-of-the-day
Best Answer
FWIW, I found this answer trying to fix this same issue. It seems that Microsoft broke or otherwise disabled Bing Desktop in favor of Bing Wallpaper (on Windows 7 at least) for wallpaper rotation. The steps above didn't help me, but I uninstalled Bing Desktop and install Bing Wallpaper (https://www.microsoft.com/en-us/bing/bing-wallpaper) and now I have my backgrounds again.