Reading this post
I changed the the routing address of the packet forwarder to: router.as.thethings.network
Described in this page:
https://www.thethingsnetwork.org/docs/gateways/packet-forwarder/semtech-udp.html
It should only work for asia 923 MHz, but it also seems to work for the india band. I now get a reply on 866.550 MHz. And that is correct