unable to use $match operator for mongodb/mongoose aggregation with ObjectId

Question

Relatively Simple Scenario:

I have this Voucher object which has a user property (of type ObjectId). I want to get the sum of

Answer 1

Turns out the casting of the ObjectId seemed to be the issue. It was being cast using the Schema type Object Id mongoose.Schema.Types.ObjectId when it needed to be just a pure ObjectId mongoose.Types.ObjectId.