Can't correlate shader source in profiler

I’m a new Nsight user.
My application compiles hlsl into .h files which are included at build time into my application.
I’m building with Visual Studio with a and the flags /Zi, /Od are set.
I’ve also added the source directory to via tools->options->search paths and allowed searching of subdirectories.
When I look at Frame Debugger->Linked Programs, the source files of my shaders are listed.

When I run shader profiler and capture a frame, in the Shader Profiler window, the source is only available as “sm5 dxbc” and the hot spots viewer tells me “Unable to show intermediate/high level hot spots as no high level source is available for the current selection”
The correlation column says “unsupported” for all shaders.
However if I click on “edit shader” the source is viewable, and editable.
What can I do to be able to view hotspots with source code?
I’m on 2023.1.1.0, using an rtx 2080, API is dx12.

Fwiw I’ve managed to work around the problem by moving my shaders to SM 6 and using /QEmbed_debug the debug information is picked up.
I’d still be really interested to learn how I could have got this working using fxc.exe