Have you enabled DNS resolution in Kiwi Syslog Server?
Setup > DNS Resolution > "Resolve the IP address of the sending device"
Thanks for the suggestion. I already had the 'Resolve the IP address of the sending device ticked'
I'm not sure I understand the problem then.
Rather than spend a lot of time with back-and-forth's on thwack, perhaps you could raise a support ticket?
There may be some other issue with your configuration.