Azure FHIR server creating a patient

Question

I'm trying to get this Fit on FHIR project working, and I got stuck creating a new patient after the user confirmed access to GoogleFit data. This is the code for creating a new patient.

if (patient == null) {
  patient = await _resourceManagementService.EnsureResourceByIdentityAsync < Patient > (
    platformIdentifier,
    platformSystem,
    (p, id) => p.Identifier = new List < Identifier > {
      id
    });

  identifierToAdd = new Identifier(externalSystem, externalPatientId);
}

where _resourceManagementService is of type Microsoft.Health.Extensions.Fhir.Service.ResourceManagementService

The parameters passed to the function are:

string platformIdentifier = 000000000000000000000 (Google Subject frow JWT)

string platformSystem = https://accounts.google.com

EnsureResourceByIdentityAsync method makes two requests:

1. HTTP GET - to check if a resource exists.
2. HTTP PUT - If a resource doesn't exist, it creates it

When the PUT request is executed, the FHIR returns this error: BadRequest: Conditional operation on Patient was not attempted because search criteria was not selective enough

What am I doing wrong?