What kind of switches are you using?
By chance…Cisco? And if Cisco, are vPCs being used? Are you STIGing the switches?
A number of things come to mind
1. check the switches and make sure GARP has not been disabled. Could be the switch or the next switch uplink. Usually the modification is on a vlan
2. if using Cisco vpc, make sure that peer-gateway is in the vpc domain configuration