Embedded app blocked from accessing cross origin frame even after setting frame ancestors CSP

[ksoenandar]

I'm getting the following error in my embedded app as I try to instantiate AppBridge

Blocked a frame with origin "https://<abcxyz>.ngrok.io" from accessing a cross-origin frame.

I've set the frame ancestors directive of my apps per the instructions here https://shopify.dev/apps/tools/app-bridge/getting-started. Can anyone point out what I'm doing wrong here?