Unable to get IP from my own MS DHCP Server when using SSID in TUNNEL MODE and VLANs

Unable to get IP from my own MS DHCP Server when using SSID in TUNNEL MODE and VLANs

The scenario:

FortiAP 231F  6.4.7  on VLAN 700

Fortigate 6.4.7 controller on VLAN 700

MS DHCP Server on VLAN500 and several scopes, for several SSIDs, 300, 301, 400, etc (tested Win2012R2 or Win2019)

3COM Switch 2620 VLAN500 untagged and tagged VLANs 300, 301 and 400 for the AP ports

Work Ok on BRIDGE MODE

We currently have a RUCKUS solution, workking perfectly, flawslessly, for more than 5 years and we´re planning to replace Ruckus, using FortiAp231F.  MS DHCP working fine, no problems at all

What´s happening: 1) Based on packet capture, we can see the DISCOVER, asking for IP, we can see an OFFER and nothing more

2) dhcprelay debug 255 is showing:

(xid:d0c789d1) got a DHCPDISCOVER (xid:d0c789d1) Warning! can't get server id from client message Insert option(82), len(12) found route to 10.121.60.4 via 10.121.62.250 iif=59 oif=12/port4, mode=auto, ifname= (xid:d0c789d1) forwarding dhcp request from 10.121.62.2:67 to 10.121.60.4:67 (xid:d0c789d1) L2 socket: received request message from 0.0.0.0:68 to 255.255.255.255 at CNS-MOBILE (xid:d0c789d1) got a DHCPDISCOVER (xid:d0c789d1) Warning! can't get server id from client message Insert option(82), len(12) found route to 10.121.60.4 via 10.121.62.250 iif=59 oif=12/port4, mode=auto, ifname= (xid:d0c789d1) forwarding dhcp request from 10.121.62.2:67 to 10.121.60.4:67

We already tried to enable the option-82 informations on SSID, sending more info to DHCP, , no luck