Firewall Checker Internal Server Error

[MusicLab]

Good morning,
3cx v15.5 (Elastix 5) give me this error when i try to do a Firewall Check

Internal Server Error(500)
System.ArgumentNullException: Value cannot be null.
Parameter name: address
at System.Net.IPEndPoint..ctor(IPAddress address, Int32 port)
at ManagementConsoleJS.Services.fwc.FirewallChecker.CreateTests(ApplicationConfiguration appcfg)
at ManagementConsoleJS.Services.fwc.FirewallChecker..ctor(ApplicationConfiguration appcfg, IServiceManager svcmgr)
at ManagementConsoleJS.Services.FirewallService.Start()
at lambda_method(Closure , Object , Object[] )
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__28.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__18.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.AspNetCore.Builder.RouterMiddleware.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at ManagementConsoleJS.Middleware.ExceptionWrapperMiddleware.d__3.MoveNext()

 

[YiannisH_3CX]

Hello @MusicLab

What is the exact build number of your PBX? You can see that on the Dashboard under the Information column next to the licence tab. Also do you face this issue only with the firewall checker?
Is this a new installation an upgrade or a restore from backup? What is the OS you installed the PBX on? h