Unable to delete Activity Type

When I try to delete an activity type, I get the following error:

Account: Team Foundation Server
User: AGLC\CManners
Version: 4.15.0.21924
EventTime: 2018-09-26T08:15:25-06:00

An error occurred while handling your request.
at method: RemoveActivityType
Message: Cannot delete Activity Type 2daa2b1b-11c0-e811-80e7-005056b7365e. Please contact support.

StackTrace:
at TimetrackerOnline.JointCodebase.BusinessLayer.Config.ActivityTypes.ActivitySettingsProvider.RemoveActivityType(ActivityTypeSetting activityTypeSetting, ActivityTypeSetting replacement, Guid projectId) in C:\build-agents\BuildAgent-git-1\_work\29\s\TimetrackerOnline\TimetrackerOnline.BusinessLayer\Config\ActivityTypes\ActivitySettingsProvider.cs:line 74
at TimetrackerOnline.Controllers.ConfigurationController.DeleteActivityType(Guid deleting, Nullable`1 replacement) in C:\build-agents\BuildAgent-git-1\_work\29\s\TimetrackerOnline\TimetrackerOnline.Web\Controllers\ConfigurationController.cs:line 1209
at lambda_method(Closure , ControllerBase , Object[] )
at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f()

Help!