Hi Oscar,
by default the aggregate will include all AS numbers from all of the contributing paths which as you can see in your output results in very long AS path which is the trigger for the route being hidden.
As per https://www.juniper.net/documentation/en_US/junos/topics/concept/policy-aggregate-routes.html
the route will be hidden when the AS path of an aggregate route—built from contributing routes— is more than half of the maximum BGP packet size (4096 bytes). Such AS paths have the OverflowASPathSize flag set for them - which is what you will likely see at the end of the AS path list in the hidden extensive output as in the example below
root@R1# run show route 0 hidden extensive
AS path: {222 330 <snip> 64345 64382} ? (LocalAgg OverflowASPathSize)
You can overcome this by changing the default behavior using this command "set routing-options aggregate defaults brief", applying it only to the default route "set routing-options aggregate route 0/0 brief" or configuring static AS path to the route.
i.e.
root@R1# set routing-options aggregate route 0.0.0.0/0 as-path path 111
root@R1# run show route 0 extensive |match "path|pref"
*Aggregate Preference: 130
AS path: 111 I
or
root@R1# set routing-options aggregate route 0.0.0.0/0 brief
root@R1# run show route 0 extensive
*Aggregate Preference: 130
Next hop type: Reject
Address: 0x9292a44
Next-hop reference count: 3
State: <Active Int Ext>
Local AS: 111
Age: 39:47
Validation State: unverified
Task: Aggregate
AS path: ? (LocalAgg Atomic)
Flags: Brief Depth: 0 Active
AS path list:
AS path: 222 330 601 82 198 26 I (Originator)
AS path: 222 I (Originator)
Cheers,
Radek