There are a few things that could try:
- Drop and re-create your private keys in the Google Console.
- Share one of the calendars from within the Google Calendar of the service account owner (googleaccounts@quirk.biz) with the SERVICE_EMAIL address.
- Do not try to impersonate an account. Remove
setServiceAccountUser(SERVICE_ACCOUNT_USER)
Be sure to use the SERVICE_EMAIL for the
.setServiceAccountId(SERVICE_EMAIL)
as you have correctly done. Google's documentation is not clear on this but using the Service Account ID will not work.
Good Luck!