After looking over my Project Settings (again), I noticed that the Company Distinguished Name was set to possibly a localized version. Additionally, after wiping the project clean, I inadvertently used RvBGames instead of the Store version, which has a numeric value prepended to it: <99999>RvBGames.
I reverted back to the previous version of the XSAPI (20170107), and now I’m repacking again using UWP64. Hopefully this will work.
Can the XSAPI calls work under the Debug build? They don’t work within the Editor.