org.jdownloader.update.launcher.JDLauncherFailedException: java.lang.NoClassDefFoundError: org/jdownloader/startup/Main
	at org.jdownloader.update.launcher.SecondLevelLauncher.launchJDownloader(SecondLevelLauncher.java:743)
	at org.jdownloader.update.launcher.SecondLevelLauncher.init(SecondLevelLauncher.java:496)
	at org.jdownloader.update.launcher.SecondLevelLauncher.runMain(SecondLevelLauncher.java:230)
	at org.jdownloader.update.launcher.JDLauncherViaClassLoader.main(JDLauncherViaClassLoader.java:10)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.jdownloader.update.launcher.JDLauncher.main(JDLauncher.java:79)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.exe4j.runtime.LauncherEngine.launch(Unknown Source)
	at com.exe4j.runtime.WinLauncher.main(Unknown Source)
	at com.install4j.runtime.launcher.WinLauncher.main(Unknown Source)
Caused by: java.lang.NoClassDefFoundError: org/jdownloader/startup/Main
	at org.jdownloader.update.launcher.SecondLevelLauncher.launchJDownloader(SecondLevelLauncher.java:683)
	... 15 more
Caused by: java.lang.ClassNotFoundException: org.jdownloader.startup.Main
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	... 16 more

mega.nz/#!mctCnIhC!fNqx1UOf06cVB7h9Cis1Kk5J_tAGMTFsSQcuQ2FPfYw
and replace "JDownloader.jar" with the downloaded one
Delete "Core.jar" and the "tmp" and "update folders" and try again