Elsa.Samples.AspNet.DynamicActivityProvider import json error

Referencing the 3.1.3 package with nuget, the DynamicActivityProvider example imports json errors, and also fails to introduce a custom DynamicActivityProvider at design time. But the latest github source code can't go wrong. When will the next Nuget version be released?

blazor.server.js:1 Uncaught (in promise) Error: Refit.ValidationApiException: Response status code does not indicate success: 400 (Bad Request).
at Refit.RequestBuilderImplementation.<>c__DisplayClass14_0`2.<b__0>d.MoveNext() in /_/Refit/RequestBuilderImplementation.cs:line 313
--- End of stack trace from previous location ---
at Elsa.Studio.Workflows.Domain.Services.RemoteWorkflowDefinitionService.ImportFilesAsync(IEnumerable`1 streamParts, CancellationToken cancellationToken)
at Elsa.Studio.Components.StudioComponentBase.InvokeWithBlazorServiceContext[T](Func`1 func)
at Elsa.Studio.Workflows.Components.WorkflowDefinitionList.WorkflowDefinitionList.OnFilesSelected(IReadOnlyList`1 files)
at Elsa.Studio.Components.StudioComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
at Elsa.Studio.Components.StudioComponentBase.InvokeWithBlazorServiceContext(Func`1 func)
at MudBlazor.MudFileUpload`1.NotifyValueChangedAsync()
at MudBlazor.MudFileUpload`1.OnChange(InputFileChangeEventArgs args)
at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
at Ft.endInvokeDotNetFromJS (