Problem:

Traffic passes through to the outside/Internet on SRX, but the dhcp server does not assign ip addresses and you cannot ping the SRX from the inside

Solution:

The system services were blocked on the inside network. Example as follows:

show security zones security-zone trust interfaces

irb.0 {
    host-inbound-traffic {
        system-services {
            snmp;
       }
    }
}

In the above case in inside interface was set up for only passing snmp traffic to the SRX. To correct, either permit ping and dhcp (and other services as needed) or

edit security zones security-zone trust interfacesdelete irb.0 host-inbound-traffic system-services 
commit