Thanks for the configuration and the access data.
If I run ping 10.4.64.30 interface ge-1/1/5.129 works fine.
set interfaces ge-1/1/5 unit 129 vlan-id 129
set interfaces ge-1/1/5 unit 129 family inet address 10.4.1.5/24
set routing-instances Private interface ge-1/1/5.129
So the access for snmp will be inside a routing instance as mentioned by Louis.
Can you confirm that ping from routing instance alone works?
ping 10.4.64.30 routing-instance Private
If so, then all you should need to add to snmp is the following:
set snmp routing-instance-access
set snmp community NAME routing-instance Private clients 10.4.64.30
subsitute your community name for NAME.