Azure Trusted Signing, how can I digitally sign a VBA macro

I have setup Azure Trusted Signing, and everything has worked fine for the dll, exe, and msi files I've needed it for. However we have some Word Template files that contain macros that our customers require to be digitally signed, and I have not been able to successfully sign them using the Azure method.

I attempted using the command: signtool.exe sign /v /debug /fd SHA256 /tr http://timestamp.acs.microsoft.com /td SHA256 /dlib C:\CodeSigning\bin\x86\Azure.CodeSigning.Dlib.dll /dmdf C:\CodeSigning\metadata.json "C:\file.dotm"

initially it complained that the file type was unsupported, so I followed the instructions for installing the Microsoft Office Subject Interface Packages for Digitally Signing VBA Projects : https://www.microsoft.com/en-us/download/details.aspx?id=56617

Now when I run the above command, it does say its successful "Signing completed with status 'Succeeded' in 2.6279078s", however when I do a signtool.exe verify C:\file.dotm, it says there is no signature found. And indeed when I open the word template and look at the Digital Signature setting it says [no certificate].

Can anyone help me here?