Well, that's because the Int32Converter class is not for Json. You have to use a class that derives from JsonConverter<t>. The Int32Converter class does not do that. I mean, look at the namespace the class sits in: System.ComponentModel. Does that sound like it has anything to do with Json?
You didn't say why you're trying to do this, so about the best I can suggest is reading up on
How to write custom converters for JSON serialization - .NET | Microsoft Learn[
^]