First look for rejects in your log file saying "no valid SA found"
Then on your active 12400 member do at bash level:
cd $FWDIR/log
vpn debug on
vpn debug ikeon
try to connect through the vpn from a device in your encryption domain
vpn debug ikeoff
vpn debug off
Now get the file $FWDIR/log/ike.elg to your PC
Open it using the IKEVIEW utility
Look for the entries for your VPN Gateway
I'm pretty sure you'll see the cause for your problems
Common causes for missing SAs are:
wrong (internal) IP used in general tab of gateway object
Rulebase not allowing IPsec communication between gateways
hth