Check that the CASH service is enabled for the subscriber:

fdpi_ctrl list --service 7 --ip <subscriber's IP>

If the ouput:

Autodetected fastdpi params : dev='lo', port=29000
connecting 127.0.0.1:29000 ...

---------------------------------
Result processing ip=1.1.1.1 : 1/0/1

That means that the service is not available to the subscriber.