The user gets created in the Telligent Community, but the error message indicates there was an auxiliary function that did not happen properly, which in turn, doesn't send back a 200 (OK) status code.
After using the v2 debug console, the problem appears to occur in the Telligent.Evolution.Messages assembly. The exception is a FormatException: Input string was not in a correct format.
It is noteworthy that this only happens in one client environment. Other environments for the same client work properly. Even other clients in the same environment work properly. All dll files are identical across clients and across environments.
I found a workaround for the error under "Membership Administration --> Configuration --> Account Settings --> New User Experience". Set "Deliver Welcome Message" to "No". When this is set to no, we get a 200 HTTP response. Obviously, we might not want this as a long-term solution, if we want to deliver an email to the new user, however.
Stack trace is:
[FormatException]: Input string was not in a correct format.
at System.Text.StringBuilder.AppendFormat(IFormatProvider provider, String format, Object[] args)
at System.String.Format(IFormatProvider provider, String format, Object[] args)
at System.String.Format(String format, Object arg0, Object arg1, Object arg2)
at Telligent.Evolution.Messages.NewUserWelcomeMessageModule.(User user, CSEventArgs e)
at Telligent.Evolution.Components.CSUserEventHandler.Invoke(User user, CSEventArgs e)
at Telligent.Evolution.Components.CSApplication.ExecuteUserEvent(Object EventKey, User user, ObjectState state, ApplicationType appType)
at Telligent.Evolution.Components.UserDataService.Create(User user, Boolean sendEmail, Boolean ignoreDisallowNames, Boolean createLocalUserOnly)
at Telligent.Evolution.Components.UserDataService.Create(User user, Boolean sendEmail)
at Telligent.Evolution.Components.UserService.Create(User user, Boolean sendEmail)
at Telligent.Evolution.Rest.Resources.Users.UserService.CreateUser(RestUser restUser)
at Telligent.Evolution.Rest.Resources.Users.UserController.Create(UserCreateRequest request)
[TargetInvocationException]: Exception has been thrown by the target of an invocation.
at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at Telligent.Evolution.Rest.Infrastructure.ActionBinding.Invoke(IController target, IRestRequest request)
at Telligent.Evolution.Rest.Infrastructure.ActionDispatcher.ProcessRequest(RequestContext context, IActionBinding binding)
at Telligent.Evolution.Rest.Infrastructure.RestHttpHandler.ProcessRequest()
at Telligent.Evolution.Rest.Infrastructure.RestHttpHandler.?(HttpContext context)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)