Hi, we've had a TAC case for a similar issue open with Check Point. In our case we had a distributed deployment (management server & separete policy server in DMZ).
The Policy server had both a local DMZ address & it received NAT'd connectioned from the public internet.
The original deployment had been done on R80.30 where the parameter referred to by Simone still existed, however all versions since then don't include that parameter in their source code.
As we upgraded from R80.30 to R81 that parameter flew out & we had a mass of disconnected clients since the external public IP disappeared from client config & devices would not even attempt to access the policy server through NAT.
The way we resolved this was through adding a new network interface to the policy server with the public IP address & entering the IP into NAT settings of the Policy Server object.
I would however STRONGLY suggest engaging with TAC prior to making any changes as mistakes in this department lead to Endpoint clients losing the IP from their configuration. And to resolve that you'd have to re-deploy or upgrade all affected installations through 3rd party tools (SCCM, etc.)