I am getting the same error on two win10 PCs.
More verbosity does not give me more information
PS C:\code\azure\AAD.fs> dotnet fake build -t registerSample
...
Starting target 'registerSample'
.> "az" account show --query tenantId --output tsv (In: false, Out: true, Err: true)
---------------------------------------------------------------------
Script reported an error:
-> BuildFailedException: Target 'registerSample' failed.
-> One or more errors occurred. (Start of process 'az' failed.)
-> Start of process 'az' failed.
-> Win32Exception: The system cannot find the file specified
PS C:\code\azure\AAD.fs> az --version
azure-cli 2.27.0
Your CLI is up-to-date.
PS C:\code\azure\AAD.fs> az account show --query tenantId --output tsv
e04f0ef7-9398-4c7e-b22d-df1496f3ad32
> dotnet --version # tried both
3.1.401 [C:\Program Files\dotnet\sdk]
5.0.302 [C:\Program Files\dotnet\sdk]