Doxygen v1.13.2, MSVS 17.13.5, Win10

Forgive me if this isn't the best place for this query. Just point me in the right direction.

Fantastic tool, BTW. I've enjoyed scaling the learning curve and have been very pleased with the output.

I've been using Doxygen for quite a few years to generate documentation for a personal educational project of mine - nothing overly ambitious or complex. I have an MSVS solution with 1 project for which I've been building HTML output. The project has a mixture of C++20 modules (.cpp/.ixx) and traditional header files (.cpp/.hpp). I've been able to resolve all warnings and errors until recently when I've started getting multiples of the subject warnings in my .cpp/.ixx module files, and only in those files, where none had occurred before. The result is that hyperlinks are not generated in the HTML output. For example, for one particular file, I get:

D:/[shortened for readabilty]/Log.ixx:88: warning: unable to resolve reference to 'Log::WriteToLog' for \ref command
D:/[shortened for readabilty]/Log.ixx:89: warning: unable to resolve reference to 'LogError' for \ref command

It doesn't matter if the references are fully qualified or not. And, notice that the reference to LogCode on line 87 isn't flagged and does work as expected.

I'm sure if I can solve these, I can solve the rest.

Edit 1 - Links removed and files attached in the zip below.
Config and Source Files.zip

What am I missing?