Failed to target upsert by query :: could not extract exact shard key

I set up a sharded database and enable sharding on the collection(EmailAddress as shardKey). And below is my code to insert in the collection (Insert only if EmailAddress doesn't exist already)

var con = MongoDBConnection.Connection;
var database = con.GetDatabase("MyDbName");
var collection = database.GetCollection<MyDbClass>("MyCollectionName");
    
var testFilter = new BsonDocument("EmailAddress", "abc@gmail.com");
var result = collection.UpdateOne(testFilter, Builders<MyDbClass>.Update
             .SetOnInsert("Name", "John Doe")
             .SetOnInsert("EmailAddress", "abc@gmail.com")
             .SetOnInsert("City", "NY"), new UpdateOptions() { IsUpsert = true });

When I run this code, It gives me this error "A bulk write operation resulted in one or more errors. Failed to target upsert by query :: could not extract exact shard key"

Any help would be greatly appreciated !