[Launcher won't instal modpacks]

Whenever I try to instal a modpack the installation loading bar pops up for a second and then disappears.

It gives me the option to delete the mod pack but where the play button should be there is still the instal button.

This is the case for all the mod packs including vanilla

I have a Mac btw

heres what the console says

[B#301] java.lang.NoSuchMethodError: org.slf4j.spi.LocationAwareLogger.log(Lorg/slf4j/Marker;Ljava/lang/String;ILjava/lang/String;[Ljava/lang/Object;Ljava/lang/Throwable;)V
[B#301]     at org.eclipse.aether.internal.impl.slf4j.Slf4jLoggerFactory$Slf4jLoggerEx.debug(Slf4jLoggerFactory.java:167)
[B#301]     at org.eclipse.aether.internal.impl.DefaultLocalRepositoryProvider.newLocalRepositoryManager(DefaultLocalRepositoryProvider.java:116)
[B#301]     at org.eclipse.aether.internal.impl.DefaultRepositorySystem.newLocalRepositoryManager(DefaultRepositorySystem.java:421)
[B#301]     at net.technicpack.utilslib.maven.MavenConnector.<init>(MavenConnector.java:67)
[B#301]     at net.technicpack.minecraftcore.install.tasks.HandleVersionFileTask.<init>(HandleVersionFileTask.java:55)
[B#301]     at net.technicpack.launcher.launch.Installer.buildTasksQueue(Installer.java:252)
[B#301]     at net.technicpack.launcher.launch.Installer$1.run(Installer.java:111)
[B#301]     at java.lang.Thread.run(Thread.java:695)
[B#301] Unhandled Exception in Thread[Thread-47,6,main]
[B#301] Starting download of http://cdn.technicpack.net/platform2/pack-icons/552547.png?1426455520, with 3 tries remaining

 

Please help