That means that gateways are not "seeing" each others packets in Sync interface. Sounds like you are connected to a switch so check that trunk between switches includes VLAN where Sync ports are connected to.
You can run
tcpdump -nni Sync port 8116 -e -c 20
and observer that you see packets originating from both gateways
listening on Sync, link-type EN10MB (Ethernet), capture size 96 bytes
21:44:10.959901 00:00:00:00:01:00 > 01:00:5e:28:fe:fa, ethertype IPv4 (0x0800), length 1330: 0.0.0.0.8116 > 192.168.254.0.8116: UDP, length 1288
21:44:10.974141 00:00:00:00:01:01 > 01:00:5e:28:fe:fa, ethertype IPv4 (0x0800), length 82: 0.0.0.0.8116 > 192.168.254.0.8116: UDP, length 40
21:44:10.974212 00:00:00:00:01:01 > 01:00:5e:28:fe:fa, ethertype IPv4 (0x0800), length 82: 0.0.0.0.8116 > 192.168.254.0.8116: UDP, length 40
21:44:10.978944 00:00:00:00:01:00 > 01:00:5e:28:fe:fa, ethertype IPv4 (0x0800), length 76: 0.0.0.0.8116 > 192.168.254.0.8116: UDP, length 34