Issues with Roboto Serif as a theme font in Windows

[puffmoike]

Apologies if this isn't the appropriate place, but I'm tearing my hair out (if you can suggest an appropriate forum to seek help that would be greatly appreciated)…

I am attempting to create a font theme using Roboto Serif and Flex for Microsoft Office apps on a Mac (creating a font theme xml file and then putting into my folder structure as per this answer on Stack Exchange).

I'm currently using "Roboto Serif" and "Roboto Flex" respectively. They are installed on my computer, and I can select either font from dropdown menus in various Office and Adobe apps.

In the Office font dropdown dialogs the theme fonts are shown as 'Roboto Serif 20pt (Headings)' and 'Roboto Flex Normal (Body)'

The Flex font is displaying as expected. But the Serif font is displaying one of the MS default fonts, Calibri, instead. I can select 'Roboto Serif' from the font dropdown (the first font displayed below the theme fonts in the attached screenshot) and it then displays correctly.

What is going on?

Is this an issue with how I have created the xml file. If so what is the correct way to refer to Roboto Serif?

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Further background…

I downloaded a version of Roboto Serif in approximately September last year that was apparently creating all sorts of issues. Trying to reopen existing files often didn't respect the Variable font settings I had used. Being relatively new to variable fonts and Microsoft Office I wasn't sure — and still aren't — whether this was a an issue with the font (Google), or with one of both of the families of apps I was trying to use (Microsoft and Adobe respectively). About two weeks ago I removed all trace of that font, and downloaded the most recent version of Roboto Serif. That appears to have solved some of my issues, but not this one.

[puffmoike]

I did an appalling job of titling this. Obviously it’s not Windows that I’m talking about, but Office on MacOS.