Agreement state is OUT_FOR_SIGNATURE but signingUrls API returns AGREEMENT_NOT_EXPOSED error

I am using the Adobe Sign REST API (v6). I have an agreement whose status is OUT_FOR_SIGNATURE. However, when I call the /agreements/{agreementId}/signingUrls endpoint, I receive the following error:json

{
  "code": "AGREEMENT_NOT_EXPOSED",
  "message": "Agreement is not exposed for signing"
}

According to the documentation, agreements in OUT_FOR_SIGNATURE state should be available for signing and the signing URLs endpoint should work.Questions:

1. Why would an agreement be in OUT_FOR_SIGNATURE but still return AGREEMENT_NOT_EXPOSED?
2. Are there any additional conditions or prerequisites (e.g., participant roles, workflow type, authentication method, or agreement settings) that must be met before signingUrls can be retrieved?
3. What is the recommended way to handle or resolve this?

apiAccessPoint is https://api.na3.adobesign.com/, for test