Known Issues

Game crashed with Offline session (1.20~)

Use below code to create offline session.

public static MSession CreateFakeSession(string username)
{
    return new MSession
    {
        Username = username,
        UUID = "2749420bc7a54b05ab622b34e61b8a79", // fake UUID
        AccessToken = "accesstoken", // fake access token
        UserType = "Mojang"
    };
}

// usage:
// var session = CreateFakeSession("username123");

ref

Can't load some texture in loading screen when using `ServerIP` option

• [BUG] When i provide server ip and port for auto connect to server on startup, the background does not load in 1.16.5 OptiFine

• Game crashed with texture related error message in 'Connecting...' loading screen.

Unfortunately, These bugs are Minecraft's bug. We can't fix.

Disabled Multiplayer button, Not authenticated with Minecraft.net

Your xbox account would block multiplay feature. Check your account settings. More Informations

Disabled Multiplayer button with Offline session in 1.16.4 and 1.16.5

https://github.com/CmlLib/CmlLib.Core/issues/85

Cannot find version <version_name>

Make sure that Mojang launcher can find your version and launch your version without any problem. CmlLib.Core will not able to find or launch the version which Mojang launcher can't.

If this exception throws even target version is in versions directory (default: <Your Minecraft Path>/versions), check version directory name, version json file file, and id property is all same. For example, assume you want to launch your own version named myversion. your version json file should be in versions/myversion/myversion.json and the id property of myversion.json should be myversion. so directory name myversion and the json file name myversion.json and the value of id property myversion is all same.

If the launcher still throw this exception, call launcher.GetAllVersions() method before launcher.CreateProcess. If you add new version into the version directory after the launcher is initialized, you should update version list through GetAllVersions() or GetAllVersionsAsync() method.

Could not create Java Virtual Machine

In a 32-bit JVM, There is limit on MaximumRamMb. Recommended value of MaximumRamMb on 32-bit JVM is 1024. More information

Error: could not open jvm.cfg

Reinstall Java. if your launcher uses MJava or JavaChecker, Remove the runtime directory (default: <Your Minecraft Path>/runtime) and install java again.

SRV Record and ServerIP

Some version of Minecraft cannot connect to server which has a SRV record when you use direct server connection feature (MLaunchOption.ServerIP).

Can't access the Minecraft window (macOS)

You have to set DockName and DockIcon in LaunchOption. If DockName is empty, you can't click or access the Minecraft window.

Example:

var launchOption = new MLaunchOption
{
    MaximumRamMb = 1024,
    Session = session, 
    DockName = "Minecraft"
};

On macOS Catalina, Minecraft works normally without the above options. Old macOS versions don't work well.

Java runtime error with OpenJDK 11 (macOS)

Old Minecraft versions don't support OpenJDK 11.

Java runtime error with OpenJDK 11 (Linux)

Use Java 8. Old Minecraft versions don't support OpenJDK 11.

To install Java 8, type the following lines in terminal:

sudo apt-get update
sudo apt-get install openjdk-8-jre

To make sure it worked, type java -version. It should return java version "1.8.0_~~~".