Manifest not found error indicates missing read permissions

The 'Manifest not found' error appears when credentials don't have read permissions for the specific repository, or when the repository name is mistyped. Docker registries are pedantic about exact repository names - 'myapp' differs from 'my-app'.

Double-check the exact repository name - verify casing and hyphens. Test that service account can pull the image with `docker pull registry/repo:tag`. Check that credentials have read permissions for that specific repository, not just the registry.