I've just installed Agile Accelerator in a sandbox, but for some reason none of the visualforce pages are loading in the org. If I navigate to a lightning record page for a given work ID I can view the record, but as soon as I hit edit or navigate to any other visualforce page, all I see is a blank white screen. I can view the pages in Classic mode, just not lightning.

I successfully installed the app in a lightning DE org this morning, so I have no idea why it would only be failing in my sandbox. Any ideas why visualforce pages would not be working in Lightning?