Do you have a firewall that drops by default?
On my machine, I have to allow 520/udp from 44.0.0.1 to 520/udp at 244.0.0.9.
I have a firewall rule but it remains at zero. It is unclear where this packet gets lost, when I run "tshark" the RIP transmission is seen, but when I insert a rule "iptables -I amprinp -p udp -s 44.0.0.1 --dport 520 -j ACCEPT" at the top of the list (this rule is selected by "iptables -A INPUT -i tunl0 -j amprinp") it too does not see any traffic. This worked OK in the past but it has suddenly stopped working some time ago, I think about two years. That happened when there was a kernel update, no other changes.
Rob