I was having the same issue, and I finally solved it by adding the "Service Account Token Creator" role to the "App Engine default service account" (PROJECT-ID@appspot.gserviceaccount...). I'm not sure why my cloud function is picking up that account instead of the "Google Cloud Functions Service Agent" but that solved this painful issue for me.
I was having the same issue, and I finally solved it by adding the "Service Account Token Creator" role to the "App Engine default service account" (PROJECT-ID@appspot.gserviceaccount...). I'm not sure why my cloud function is picking up that account instead of the "Google Cloud Functions Service Agent" but that solved this painful issue for me.
This did work for me too
Thanks!!!