1.無法連接到網絡
2.點擊安裝和更新無響
這兩種情況造成的原因都是由於被牆的原因，第一種情況有部分可以通過fq解決，第二種情況是我遇到過的 反正我全局也失敗
這里給出一個我自己用過的解決方案
查看控制台日志，中間有這么一段:
[2017-08-30 08:02:22.972] [Info] Downloading from 'https://www.xamarin.com/installer_assets/v3/409bb0941397899e59046bb54cba2bfd5cd9fd76/Mac/Universal/InstallationManifest.xml'.
[2017-08-30 08:02:22.974] [Debug] Setting download timeout for 'https://www.xamarin.com/installer_assets/v3/409bb0941397899e59046bb54cba2bfd5cd9fd76/Mac/Universal/InstallationManifest.xml' to 60s
[2017-08-30 08:02:25.436] [Info] Downloading from 'https://www.xamarin.com/installer_assets/v3/Mac/Universal/InstallationManifest.xml'.
[2017-08-30 08:02:25.436] [Debug] Setting download timeout for 'https://www.xamarin.com/installer_assets/v3/Mac/Universal/InstallationManifest.xml' to 60s
將中間的網址粘貼到瀏覽器上面那個打開失敗 下面那個可以正常打開，從里面可以查看到每個組件的下載地址
使用工具將組件下載下來安裝即可
PS:組件下載地址:
Mono Framework 5.2.0.215 https://dl.xamarin.com/MonoFrameworkMDK/Macx86/MonoFramework-MDK-5.2.0.215.macos10.xamarin.universal.pkg
Java SDK 1.8 http://download.xamarin.com/Installer/MonoForAndroid/jdk-8u101-macosx-x64.dmg
Android SDK 24.4.1 http://dl.google.com/android/android-sdk_r24.4.1-macosx.zip
NDK 10 http://dl.google.com/android/ndk/android-ndk-r10e-darwin-x86_64.bin
Visual Studio for Mac 7.1.0.1297 https://dl.xamarin.com/VsMac/VisualStudioForMac-7.1.0.1297.dmg
Xamarin.Android 7.4.0 https://dl.xamarin.com/MonoforAndroid/Mac/xamarin.android-7.4.0-21.pkg
Xamarin.iOS 10.12.0.20 https://dl.xamarin.com/MonoTouch/Mac/xamarin.ios-10.12.0.20.pkg
Xamarin.Mac 3.6.0.19 https://dl.xamarin.com/XamarinforMac/Mac/xamarin.mac-3.6.0.19.pkg
Intel® HAXM 6.0.5 https://dl.xamarin.com/Installer/haxm-macosx_v6_0_5.zip
Xamarin Profiler 1.5.5.10 https://dl.xamarin.com/profiler/profiler-mac-1.5.5-10.pkg
Xamarin Workbooks & Inspector 1.2.2 https://dl.xamarin.com/interactive/XamarinInteractive-1.2.2.pkg