You need to accept the licenses through the terminal/prompt

e.g on linux:

cd ~/Library/Android/sdk/tools/bin/

Run the sdkmanager as follows:

./sdkmanager --licenses

e.g on Windows:

cd /d "%ANDROID_SDK_ROOT%/tools/bin"

Run the sdkmanager as follows:

sdkmanager --licenses

And accept the licenses you did not accept yet (but need to).