I am having a similar issue. @felwsaerius, did you get a work around?
From 2013?! Even if he did, whatever issues he may have been hitting have probably been fixed.
Guessing I'd say thay user's ISP was not routing those IPs to him. So either the ISP had not enabled it yet or he needed VIPs on WAN they can ARP for.
Reading your other thread I would say your ISP is not routing that IP to you. Call them.