PDF Embed API not capturing Google Analytics 4 events via Google Tag Manager

We're using the Embed API to display PDFs on a website. The GA4 measurementId is set and all the custom dimensions are also configured per the documentation, yet we're not seeing any of the Adobe events come through (e.g. Load PDF, Download, Print, Hyperlink Open, etc). 

The site uses Google Tag Manager (GTM) to inject the GA4 tracker.

How can we get Adobe to play nice with GTM?