Hi,
Is the issue seen while connecting to master IAP or slave IAP?
In multi-IAP environment, make sure the client vlan is allowed on IAP's uplink as client traffic from slave IAP to master is tagged with the client
vlan.
Basically, your IAP's need to be on trunk ports which allows the vlan configured in L2 centralized scope.
Moreover, please make sure vlan is created on the controller as well.
DHCP server can be on the controller or any device upstream. We just need to ensure DHCP packet from the client can reach the DHCP server.