Hi,
It seems to be local id issue. Can you please check below settings if it works:
1: in you Android client, can you try configuring IPSec identifier same as the ikeID user in the netscreen.
2: OR User/Group name same as in IKE gateway config?
3: Are you using any local id in the IKE gateway config?
4: Strongswan is not working because it's using ikeV2.
Thanks,
Vikas