Tagged and untagged traffic

Hello guys,

I have the following scenario: MT1 ↔ Unmanaged switch ↔ MT2 ↔ Internet

MT1: 2 Virtual APs + 1 LAN port (RB411AH), names: OFFICE, GUEST
MT2: 2 LAN ports (1 for LAN, 1 for Internet)
Unmanaged switch: connect office network (computers, printers…)

MT1 and MT2 have a VLAN interface (VLAN1), configured on LAN interfaces. On MT1, I have 2 bridges: BR1 (members: LAN + OFFICE), BR2 (members: VLAN1 + GUEST)

On MT1, BR1 and VLAN1 has an IP address from different subnets. (10.1.3.10 for BR1, 10.1.26.10 for VLAN1)
On MT2, LAN has IP address: 10.1.3.1, VLAN1 has IP adress: 10.1.26.1

Wireless clients from OFFICE wlan should see the internal network (10.1.3.0) and Internet, clients from GUEST wlan should reach only the Internet (traffic from OFFICE should be untagged on LAN side, traffic from GUEST should be tagged between the 2 MT to separate the guest traffic from the office traffic).

Everything semms to be ok, but I have only untagged traffic (OFFICE netowrk works, GUEST not). What I’m missing?