DVLS server is not responding

I'm trying to add an RDM connection profile with domain authentication and the test connection fails with error:
DVLS server is not responding.
Unexpected exception

Here is the error report:

The following error was received by at 4/19/2018 11:17:18 AM
Error:
NullReferenceException - Object reference not set to an instance of an object. at Devolutions.Server.Controllers.APIControllers.V2.BackendApiController.PrepareFailedLoginResult(Guid userId, PrepareResultModel model, Boolean partialMode) at Devolutions.Server.Controllers.APIControllers.V2.BackendApiController.DoLogin(SessionContext context, String userName, String password, ClientApplicationInfo clientApplicationInfo, String twoFactorID, TwoFactorInfo twoFactorInfo, String publicIPAddress, Byte[] sessionKey, String repositoryId, Boolean partialMode, Boolean useWindowsAuthentication, String localMachineName, String localMachineUserName) at Devolutions.Server.Controllers.APIControllers.V2.BackendApiController.Login(LoginData loginData, Boolean partialMode) at lambda_method(Closure , Object , Object[] ) at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.b__9(Object instance, Object[] methodParameters) at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken) --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Controllers.ApiControllerActionInvoker.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Filters.ActionFilterAttribute.d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Web.Http.Filters.ActionFilterAttribute.d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Filters.ActionFilterAttribute.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Controllers.ActionFilterResult.d__2.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Controllers.ExceptionFilterResult.d__0.MoveNext() --- Default
Source:
Devolutions.Server



Please advise