> monitor traffic interface ae0 size 9999 no-resolve count 5 matching "udp port 162 or 162"
With this command you can only monitor traffic TO the Router itself because you can only see traffic handled by the Routing Engine, transit traffic is handled by the ASIC and therefore it not touched by the RE. If you can't see anything on ae0, then there is no traffic flowing to the Router, (maybe) only flowing THROUGH the Router.
Additionally, "udp port 162 or 162" does not make any sense. E.g. you can perform "port 162" for all traffic from/to this port.