FirebaseAuthentication.net causing build to fail

I'm really new to Xamarin and have been trying to get the FirebaseAuthentication.net (sorry i cant post links yet) library to work with a Xamarin.Forms project ; I added it as a dependency to my PCL and I get the error

 Error: Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly 'Firebase.Auth, Version=1.0.0.0, Culture=neutral, PublicKeyToken='. Perhaps it doesn't exist in the Mono for Android profile?
File name: 'Firebase.Auth.dll'
  at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Resolve (Mono.Cecil.AssemblyNameReference reference, Mono.Cecil.ReaderParameters parameters) [0x00099] in /Users/builder/data/lanes/5147/c2a33d8e/source/xamarin-android/external/Java.Interop/src/Java.Interop.Tools.Cecil/Java.Interop.Tools.Cecil/DirectoryAssemblyResolver.cs:220
  at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Resolve (Mono.Cecil.AssemblyNameReference reference) [0x00000] in /Users/builder/data/lanes/5147/c2a33d8e/source/xamarin-android/external/Java.Interop/src/Java.Interop.Tools.Cecil/Java.Interop.Tools.Cecil/DirectoryAssemblyResolver.cs:170
  at Xamarin.Android.Tasks.ResolveAssemblies.AddAssemblyReferences (Java.Interop.Tools.Cecil.DirectoryAssemblyResolver resolver, System.Collections.Generic.ICollection`1[T] assemblies, Mono.Cecil.AssemblyDefinition assembly, System.Boolean topLevel) [0x0015c] in <593a6fd557984367bb21e275d0fa0659>:0
  at Xamarin.Android.Tasks.ResolveAssemblies.Execute (Java.Interop.Tools.Cecil.DirectoryAssemblyResolver resolver) [0x0019c] in <593a6fd557984367bb21e275d0fa0659>:0  (firenotes.Droid)

when I tried to build. I have tried changing project target to .NET standard, but that hasn't helped either. Couldanyone point me in the right direction, thanks