Unfortunately that feature is not supported on the QFX series.
"The Juniper Networks Junos OS implementation of PBB supports the IEEE 802.1ah standard.
Note: PBB is supported ONLY on MX Series routers or EX Series switches with Dense Port Concentrators (DPCs). PBB is not supported on routers or switches with Modular Port Concentrators (MPCs)."
Just curious: This is a service provider feature, which I would assume that you are in a service provider environment. This is not something that customers would send. They send SP a single tag or untagged, SP then add second tag 802.1q and send to their own SP 802.1ah environment. Is your customer another service provider?
Background
The IEEE 802.1ah on Provider Backbone Bridges feature encapsulates the end users traffic inside the service providers MAC header, enabling the backbone edge bridge (BEB) to support large numbers ofservice instances. This functionality is also known as MAC-in-MAC or MAC Tunneling Protocol (MTP). It also allows service providers to hide the identity of their equipment vendors by using user-specified MAC address as the tunnel source address. It also separates the user MAC address space from the provider MAC address space which means that only the edge bridges are aware of the customer MAC addresses, and that only the core bridges are aware of the provider addresses.