I ran Repair on the Visual C++ Redistributables and verified the UE 5.5 install: the problem persists.
Next tests:
I am using Dependencies to see if there are any missing dlls.
These files appear to be missing:
ext-ms-win32-subsystem-query-l1-1-0.dll
ext-ms-win-oobe-query-l1-1-0.dll
HvsiFileTrust.dll
Following the logic of the commenter in: this thread on Microsoft.com, I ignored the ext.ms- dlls and just copied one of the HvsiFileTrust.dll files that’s present elsewhere on my system into the Build directory.
Re-running Dependencies shows the same missing dlls, and the program still doesn’t run (same results when debugging in Visual Studio).
That seems like a wild goose chase.