Android sdk manager download finished with wrong checksum
Clearing the SDK Manager cache: [Tools > Options > Clear] Cache and the reloading [Package > Reload] helps. Also in some cases disabling 2 Nov 2017 Downloading Android SDK Platform-tools, revision 26.0.2. Download finished with wrong checksum. You can manually install over the current SDK toolkit (Admittedly I did it with my eyes closed and fingers crossed).