Why do I get a daemon pull access denied error login incorrect or repo doesn't exist? I know the login is correct and the repository exists

I am trying to pull a docker image by executing: docker pull xxyy/sampledb but am getting the following error:

Error response from daemon: pull access denied for xxyy/sampledb, repository does not exist or may require 'docker login': denied: requested access to the resource is denied

So I know the repository exists, because when I run aws ecr describe-images xxyy/sampledb, it returns:

 "imageDetails": [
        {
            "registryId": "123456789",
            "repositoryName": "xxyy/sampledb",
            "imageDigest": "sha256:26c8956921bc5b3530fea3de762a6b0891884fec2760",
            "imageTags": [
                "latest"
            ],
            "imageSizeInBytes": 5037757,
            "imagePushedAt": "2022-09-05T11:45:40+01:00",
            "imageManifestMediaType": "application/vnd.docker.distribution.manifest.v2+json",
            "artifactMediaType": "application/vnd.docker.container.image.v1+json",
            "lastRecordedPullTime": "2023-08-09T11:03:44.123000+01:00"
        },

And I log into the aws erc successfully, and I know I have the right login, because the ending of the login is 123456789.dkr.ecr.us-east-1.amazonaws.com

Any ideas why I am being returned that error?

You're missing the registry name in your image pull.

docker pull 123456789.dkr.ecr.us-east-1.amazonaws.com/xxyy/sampledb

If you do not specify a registry, it will default to Docker Hub.