Realm Sync: failed to validate upload changesets

[Jacqueline_Arokiaswa (Jacqueline Arokiaswamy)]

Hi,
I have an existing iOS App using local Realm. I enabled sync on MongoDB realm and setup the schema for the same(Under Rules). I am seeing the following log error:
"Ending session with error: failed to validate upload changesets: could not find primary key “_id” in target table schema with name “Tag” (ProtocolErrorCode=212) "

My Schema is:

{
  "title": "Tag",
  "bsonType": "object",
  "required": [
    "id",
    "userId"
  ],
  "properties": {
    "userId": {
      "bsonType": "string"
    },
    "id": {
      "bsonType": "string"
    },
    "text": {
      "bsonType": "string"
    },
    "createdAtDate": {
      "bsonType": "date"
    },
    "lastModifiedDate": {
      "bsonType": "date"
    }
  }
}

The swift code model code is:

[Jay (Jason Wooten)]

@Jacqueline_Arokiaswa

could not find primary key “_id”

And your model does not contain an _id property; only an id is shown in the object in the question