If the hiding address does not show up in the output of command fw ctl arp you did not add the manual proxy ARP correctly; see sk30197. If it does show up in the output of fw ctl arp make sure clustering is disabled under cpconfig (assuming of course it is just a single firewall and not part of a cluster). If the firewall is part of a cluster, make sure it is in an active state with cphaprob stat.
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