[Serusers] please HELP CISCO ATA not re-registers

[Humberto Atristain]

Dear Pals.

I have a 10 point VPN in the central I have  a  SER working fine , and
we have CISCO ATA´s in the branches and also in the central site, my
trouble is that if for some reason the vpn comes down , when the VPN
comes up again , the SER do not registers the ATAs , got no idea what to
do here, take in note I´m newbie and please be a little explicit.

I have tried with in ATA
SIPREG: 1 
SIPRegInterval: 360


Please Help

Regards

Humberto Atristain