Since PPTP VPN is no longer supported by Apple’s built-in VPN client on macOS Sierra and iOS 10, Draytek recommends that SSL VPN be used instead.
The SmartVPN client is available in the App Store now.

Please refer to these FAQs for more details.

Mac Smart VPN to Vigor Router - SSL VPN

SmartVPN iOS app to Vigor Router - SSL VPN

If the user prefers to use Apple's native VPN client, L2TP over IPsec should be selected to ensure interoperability with Vigor routers.

Here are additional Draytek FAQs for your reference.

iPhone to Vigor Router - L2TP over IPsec

How to establish VPN connection from Mac OS to Vigor Router via L2TP over IPSec?