Running cros tryjob on a cloudtop machine fails with cipd errors:

/usr/local/google/home/bmgordon/chromiumos/.cache/cipd/03f354ad7a6031c7924d9b69a85f83269cc3c2e0 ensure -root /usr/local/google/home/bmgordon/chromiumos/.cache/cipd/packages/infra/tools/authutil/linux-amd64 -list /tmp/tmpnrUCaS
 [P13932 18:51:25.398 client.go:372 DEBU 001] cipd: resolving version "latest" of "infra/tools/authutil/linux-amd64"...
 [P13932 18:51:25.404 remote.go:102 WARN 002] cipd: connectivity error (Get https://chrome-infra-packages.appspot.com/_ah/api/repo/v1/instance/resolve?package_name=infra%2Ftools%2Fauthutil%2Flinux-amd64&version=latest: metadata: GCE metadata "instance/service-accounts/default/token" not defined)
...
[P13932 18:51:43.422 main.go:553 ERRO 015] Error while updating packages: Request to the backend failed after multiple attempts

cmd=['/usr/local/google/home/bmgordon/chromiumos/.cache/cipd/03f354ad7a6031c7924d9b69a85f83269cc3c2e0', 'ensure', '-root', '/usr/local/google/home/bmgordon/chromiumos/.cache/cipd/packages/infra/tools/authutil/linux-amd64', '-list', '/tmp/tmpnrUCaS']

/tmp/tmpnrUCaS contains one line:
infra/tools/authutil/linux-amd64 latest

If I run the exact same command, I get the same error.  If I run the same command using ~/bin/depot_tools/cipd instead of 03f354ad7a6031c7924d9b69a85f83269cc3c2e0, it appears to work fine.  If I replace 03f354ad7a6031c7924d9b69a85f83269cc3c2e0 in the path above with a symlink to ~/bin/depot_tools/cipd and copy the other files into the directory, it also works fine.

Is there something funny about a cloudtop machine that makes the cipd version used by cros not work?