Hi guys,
I encounter the very same issue. Attached you can find the logs (java.lang.IllegalArgumentException: object is not an instance of declaring class)
Thanks a lot!
[B#353] 2017/10/07 12:48:16 [INFO] OS: mac os x
[B#353] 2017/10/07 12:48:16 [INFO] Identified as osx
[B#353] 2017/10/07 12:48:16 [SEVERE] java.lang.IllegalArgumentException: object is not an instance of declaring class
[B#353] 2017/10/07 12:48:16 [SEVERE] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[B#353] 2017/10/07 12:48:16 [SEVERE] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
[B#353] 2017/10/07 12:48:16 [SEVERE] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
[B#353] 2017/10/07 12:48:16 [SEVERE] at java.base/java.lang.reflect.Method.invoke(Unknown Source)
[B#353] 2017/10/07 12:48:16 [SEVERE] at net.technicpack.launcher.LauncherMain.startLauncher(LauncherMain.java:299)
[B#353] 2017/10/07 12:48:16 [SEVERE] at net.technicpack.launcher.LauncherMain.main(LauncherMain.java:194)
[B#353] 2017/10/07 12:48:16 [SEVERE] Unhandled Exception in Thread[main,5,main]
java.lang.IllegalArgumentException: object is not an instance of declaring class
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base/java.lang.reflect.Method.invoke(Unknown Source)
at net.technicpack.launcher.LauncherMain.startLauncher(LauncherMain.java:299)
at net.technicpack.launcher.LauncherMain.main(LauncherMain.java:194)