Shopify - The given key was not present in the dictionary

[PixelDevelopers]

I have attempted to use you project to authenticate with Shopify and allow users to sign in.
However, whenever I try and use this method I get the below error.

[KeyNotFoundException: The given key was not present in the dictionary.]
System.Collections.Generic.Dictionary`2.get_Item(TKey key) +12834479
Owin.Security.Providers.Shopify.ShopifyAuthenticationHandler.ApplyResponseChallengeAsync() +653
Microsoft.Owin.Security.Infrastructure.d__40.MoveNext() +170
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Security.Infrastructure.d__39.MoveNext() +271
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Security.Infrastructure.d__34.MoveNext() +158
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Security.Infrastructure.d__5.MoveNext() +659
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.d__7.MoveNext() +179
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Security.Infrastructure.d__5.MoveNext() +519
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Security.Infrastructure.d__5.MoveNext() +519
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.d__7.MoveNext() +179
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.d__12.MoveNext() +180
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult ar) +69
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.EndFinalWork(IAsyncResult ar) +64
System.Web.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +429
System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +50
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +163