For others reference regarding Lenovo Yoga 720 13 (IKB) - From support tech David:
"Looking at the specifications of the Yoga 720 (https://www3.lenovo.com/us/en/laptops…) it seems that both USB-C ports have the same functionality (2 x USB Type-C with ThunderboltTM).
However, the manual here –> https://images-eu.ssl-images-amazon.c… only mentions that front USB-C port supports video output, while the back USB-C port reads: “AC power adapter jack. Connects to the AC power adapter. Note: For Lenovo YOGA 720-13IKB, the AC power adapter jack is compatible with Type-C USB 3.0 devices” (pages 10 and 11 of the manual)."
In short - only the front port works with a DisplayLink connection. If you have this model you should also review this: