The OS you're using and its version Windows 10 Pro, version 1809, OS Build 17763.55 This is the so called "October Update"

The name and version of the Cubecoders product you are using AMP

A description of the issue you are having Attempting to start a new Minecraft Bedrock (Alpha) server fails after upgrading Windows to the October Update. The log shows:

[Core:admin Error]     : [0] (ArgumentNullException) : Value cannot be null.
Parameter name: fileName

I have previously had a Bedrock server active on this computer successfully for several weeks.

Steps to reproduce the issue (for bugs in particular) I created a new user called "AMP" as suggested in the instructions. I logged in and installed AMP. I created a new Minecraft instance (stand-alone, no ADS). I setup a basic survival game. I clicked the Start button. The buttons (Start/Update) disappear and a popup appears with a Core Admin error message (see below).

What you have tried so far to resolve the issue and what happened. Complete un-install/re-install of AMP. Updated Java to v8, update 191. Installed latest nightly build (as of 11/12). The Minecraft server will run when executed manually and is joinable.

A paste of any relevant output from the log file for a given AMP instance (where applicable). Full log from a fresh install:

[15:20:44] [System Info]          : Starting AMPService version (TN/SR6), built 10/11/2018 12:09
[15:20:44] [System Info]          : OS: Windows / x86_64
[15:20:44] [System Info]          : AMP Instance ID: c4821633-5d5c-4f62-89f8-450525c2fc9d
[15:20:44] [System Info]          : Checking for AMP updates...
[15:20:44] [GSMyAdmin Info]       : Loaded MinecraftModule version by CubeCoders Limited
[15:20:44] [GSMyAdmin Info]       : Loaded EmailSender version by CubeCoders Limited
[15:20:45] [GSMyAdmin Info]       : Loaded FileManager version by CubeCoders Limited
[15:20:45] [GSMyAdmin Info]       : Loaded PushBulletPlugin version by CubeCoders Limited
[15:20:45] [GSMyAdmin Info]       : Loaded LocalFileBackupPlugin version by CubeCoders Limited
[15:20:45] [GSMyAdmin Info]       : Licence Present: AMP Professional Edition (Licenced to ***************)
[15:20:45] [GSMyAdmin Info]       : Webserver started on
[15:20:45] [WebServer Warning]    : RouterTimer@10Hz with 2 jobs started
[15:21:40] [GSMyAdmin:Anonymous Activity] : Authentication attempt for user admin from
[15:21:40] [GSMyAdmin:admin Activity] : Authentication success
[15:22:30] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.MinecraftSettings.ServerType to 210
[15:22:33] [System:admin Activity] : Updating the application.
[15:23:27] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.MinecraftSettings.LevelName to DaftCraft
[15:23:33] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.MinecraftSettings.GenStructures to True
[15:23:34] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.MinecraftSettings.EnableNether to True
[15:23:57] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.GameSettings.Difficulty to 2
[15:23:59] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.GameSettings.EnableMonsters to True
[15:23:59] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.GameSettings.EnablePVPCombat to True
[15:24:00] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.GameSettings.EnableNPCs to True
[15:24:01] [GSMyAdmin:admin Activity] : Changing setting MinecraftModule.GameSettings.EnableAnimals to True
[15:24:19] [System:admin Activity] : Starting the application.
[15:24:20] [System:admin Activity] : Starting the application.
[15:24:20] [GSMyAdmin:admin Warning] : Returned exception from API call
[15:24:20] [Core:admin Error]     : [0] (ArgumentNullException) : Value cannot be null.
Parameter name: fileName
[15:24:20] [Core:admin Error]     :    at IO.FileInfo..ctor(String fileName)
   at MinecraftModule.MinecraftApp.StartGameServer(Boolean autoRetry)
   at GSMyAdmin.WebServer.WebMethods.Start()
   at GSMyAdmin.WebServer.WebAttributes.InvokeMethod(String MethodName, JObject Data, IHttpRequest request, IWebSession Session, WebMethodsBase MethodsClass, String RawRequest)
   at GSMyAdmin.WebServer.APIService.InvokeAPI(IHttpRequest request, IWebSession Session, JObject Data, String RequestModule, String RequestMethod, String RawRequest)

For AMP, which application module you're using Minecraft