Yes, we are having the same issue. I spent all morning trying to get this working and couldn’t. When the GET API call is initiated the status always returns “starting” and hence it doesn’t find an output file. My initial GET calls was pulling all the predictions as a list, but was able to figure out how to initiate the call for a specific prediction.
I discovered about webhook after reading your post, but couldn’t figure out a way to setup the webhook on Replicate. I moved onto another app I am working on, as this was consuming too much time. After pixel pushing, I think this is the most frustrating part of app development - the output is right there - you can see it and you want to grab it, but can’t :).
How are you failing on the webhook call?