Deployment to app engine flex environment fails with following message:

ERROR: (gcloud.app.deploy) PERMISSION_DENIED: You do not have permission to act as '***@appspot.gserviceaccount.com'
"app-deploy": - '@type': type.googleapis.com/google.rpc.ResourceInfo
"app-deploy":   description: You do not have permission to act as this service account.
"app-deploy":   resourceName: egate-digi-development@appspot.gserviceaccount.com
"app-deploy":   resourceType: serviceAccount

where *** is the project Id

Note the command is run from the google Cloud Build step using command

gcloud app deploy \
    --quiet \
    --version $APP_VERSION \
    --project *** \
    app.yaml cron.yaml

The google build service has following roles assigned:

App Engine Admin
Cloud Build Service Account
Cloud Scheduler Admin
Cloud SQL Editor

The same deployment worked without issues last week. Only change from our side was switching the repository for the build trigger.

There is related question on Stack Overflow: https://stackoverflow.com/questions/64236468/cloud-build-fails-to-deploy-to-google-app-engine-you-do-not-have-permission-to which indicates the issue started to manifest recently.