botbuilder-dotnet: Cannot use AzureTableStorage to persist ConversationState for dialogs

Trying to use Azure table storage to handle dialog state. File Storage works, but not Azure Storage.

When using this code for dialogs:

   public class EchoBot : IBot
    {
        private readonly DialogSet dialogs;
        public EchoBot()
        {
            dialogs = new DialogSet();
            dialogs.Add("greetings", new WaterfallStep[]
            {
                async (dc, args, next) =>
                {
                    // Prompt for the guest's name.
                    await dc.Prompt("textPrompt","What is your name?");
                },
                async (dc, args, next) =>
                {
                    await dc.Context.SendActivity($"Hi {args["Text"]}!");
                    await dc.End();
                }
            });

            // add the prompt, of type TextPrompt
            dialogs.Add("textPrompt", new Microsoft.Bot.Builder.Dialogs.TextPrompt());
        }

        public async Task OnTurn(ITurnContext context)
        {           
            // This bot is only handling Messages
            if (context.Activity.Type == ActivityTypes.Message)
            {
                // Dialogs
                var state = ConversationState<Dictionary<string, object>>.Get(context);
                var dc = dialogs.CreateContext(context, state);

                await dc.Continue();

                if (!context.Responded)
                {
                    await dc.Begin("greetings");
                }
            }
        }
    }

In startup.cs this works:

var dataStore = new FileStorage("c:/temp");
options.Middleware.Add(new ConversationState<Dictionary<string, object>>(dataStore));

But this doesn’t

IStorage dataStore =
new Microsoft.Bot.Builder.Azure.AzureTableStorage("DefaultEndpointsProtocol=https;AccountName=aihelpwebsitestorage;AccountKey=**account Key**;EndpointSuffix=core.windows.net","helloworldbotsimpledialog");

options.Middleware.Add(new ConversationState<Dictionary<string, object>>(dataStore));