Matt,
I am having the exact same issue as Bhoomi. I used the ping syntax on the link you provided and ping was good....
root> ping 128.0.0.16 routing-instance __juniper_private1__
PING 128.0.0.16 (128.0.0.16): 56 data bytes
64 bytes from 128.0.0.16: icmp_seq=0 ttl=64 time=0.273 ms
64 bytes from 128.0.0.16: icmp_seq=1 ttl=64 time=0.606 ms
However, I also cannot see the ge- interfaces. I tried lite-mode, but that didn't work either. I have plenty of resources, I'm running on a Dell Blade Chassis, the Dell m1000e series blade. In my case I've allocated no less than 4 x CPUs and at least 8-10 GB of memory ---- but still cannot see interfaces.
I just don't get it. This is really bothering me because I desparately want to incorporate vMX into my Service Provider lab topology.

Somebody help me figure this out ... if you do ... I'll call you the coolest engineer in the world for 10 more years ---- em hem --- if I remember in 10 years that is 🙂