Set mailto links to open in Outlook PWA

We've recently moved across to the Microsoft Outlook "progressive web app" (PWA).

Originally when I was clicking "mailto" hyperlinks on websites, macOS would open Mail. I have managed to change the default mail app over to the Outlook PWA. The problem is, however, that now when I click those "mailto" hyperlinks, Outlook PWA is opening, but not to a "new email" window. Instead, it just opens to the email inbox.

Does anyone know how to get the "mailto" functionality working on Outlook PWA, just like it does with Outlook desktop?