Why doesn't my post purchase extension debug in Chrome?

I’m having an issue trying to debug post purchase extensions.

I have a basic post purchase extension exposed via ngrok. Its displaying fine in chrome using the shopify plugin and static data. I have an issue somewhere in my code when I attempt to fetch data from my server but I haven’t been able to step in to the code while the extension is running to debug it.

I’m using vscode and running shopify extension serve to expose the app extension. I attach vscode to the terminal session and it looks like its attached but when I click through a purchase in chrome my breakpoints are not hit. I also don’t see any console output.

Any ideas how to attach, step through and get console output so that I can debug the issue?