At first, download the Android SDK manually from the bottom of this page
Secondly, create a new folder named "android-sdk" and place downloaded tools folder inside the android-sdk folder
Now place the "android-sdk" folder to the Home directory and show the location to the Axway Appcelerator Studio>>Preferences>>Studio>>Platforms>Android>Android SDK Home
Then click on Install SDKs>> Now select android 6.X.X, 7.X.X,8.X.X and install those packages.
If you face any issue then try to setup android SDK via the terminal.
- appc ti config android.sdk <SDK location>
- appc ti setup android
- And restart PC
Also, take a look android SDK installation guide -
Hope this helps.