EMIS ICE Access in HSCN

Hi all. We have got EMIS Live Frontend Environment access in HSCN in our AWS EC2 . We are connecting to HSCN through supplier. We have been allocated NHS IPAM /29 block where we have allocated one IP for EMIS. We have allowed IP ranges given by EMIS through our firewall and are able to install EMIS for our Organisation ID. Now when trying to make online test request for booking tests through EMIS, we are not able to connect to ICE. Is there something that we have missed?. Do we have to get our NHS IPAM block whitelisted by ICE for us to connect to ICE? Hoping for your guidance on this matter. Thanks