OK. Here is something interesting...
In VS2019, if I select Help...Compilers & Libraries...Intel C++ Compiler,
A browser opens minimised which has two tabs open:
the first tab is a link to the Fortran Compilers reference documentation
The second tab is a link to the C++ compiler Reference documentation.
This makes up for the lack of response when selecting
Help...Compilers and Libraries...Intel Fortran Compiler!
how to explain this when the C-compiler Help is in
C:\Program Files (x86)\Intel\oneAPI\compiler\2021.4.0\windows\documentation\en\compiler_c
and the Fortran compiler help files are in C:\Program Files (x86)\Intel\oneAPI\compiler\2021.4.0\windows\documentation\en\compiler_f.