If you can reach both clusters but not go through them, and assuming that the traffic is being allowed by the Firewall Policy on both, either you have a NAT configuration issue or possibly some kind of routing problem involving the NAT addresses you are trying to use. You'll need a packet capture on the clusters to see exactly what is going on, as the Check Point traffic logs will gladly show you exactly how traffic is being allowed and NATed, but those same logs are not really designed to reveal routing problems.
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