Flurl Http FlurRequest reference not resolving

I am building a Xamarin.Forms application (.NETStandard 2.0) and one of my projects is using Flurl.Http.

My Android and UWP head projects are building fine but my IOS project is failing to build with error:

MyApp.App.iOS/MTOUCH: Error MT2002: Failed to resolve
"Flurl.Http.FlurlRequest" reference from "Flurl.Http, Version=2.3.2.0,
Culture=neutral, PublicKeyToken=null" (MT2002)