DHCP Relay through IPsec Tunnel

Hello, this is a diagram of my current situation right now.

In SITE A, a Mikrotik router connected to a Fortigate in site B via IPSEC tunnel. I would like to make DHCP Relay work to my Windows DHCP server SITE B, but for the moment I’m not able to do it.

The IPSEC Tunnel is working properly

I can ping from LAN Site A to DHCP server Site B
Wireshark on DHCP Server makes me see traffic between A and B, but nothing from DHCP is showing

In my fortigate, I opened all policies to avoid issues.

I read Mikrotik documentation but there is no example about my situation.

Many thanks for your help !

Fixed.

/ip route add dst-address=192.168.B.45 gateway=bridge1

THanks