Unableto create FHIRJson node

I am getting this error while trying to create FHIRJsonnode in c#.

{“Root object has no type indication (resourceType) and therefore cannot be used to construct an FhirJsonNode. Alternatively, specify a nodeName using the parameter.”}

Although I have verified that object created for it has typename mentioned still giving this exception.
Does anyone have any idea about this?

Can you show me the actual code you use & (parts of) the Json data you are using so I can help diagnose the problem?

Sure. I am using C#.
Here is the code:
Observation observe = model.ConvertToFHIRObservation();
var client = FHIRAuthService.GetClientObject();
Observation response = client.Create(observe);

In function ConvertToFHIRObservation() I am creating observation for a vital we are passing through Json String.
The error appears when we try to create observation in FHIR server.
And this error appear randomly.

e.g Json string we are sending:
Blood_oxygen:{“PatientId”:“19629d16-ac87-4ed7-a262-6d0801943245”,“DataType”:“Spo2Data”,“SyncType”:“OnRequest”,“DeviceId”:“F9:2A:C6:14:E7:41”,“DataEnd”:“NO”,“Data”:{“arraySpo2Data”:[{“date”:“2021.05.17 11:21:14”,“spo2Data”:“98”}]}}