FortiLink issue: FortiSwitch detected but always Down

Hello,

We have a FortiSwitch connected to a Huawei core switch, and we want to manage the FortiSwitch through our FortiGate using FortiLink.

We configured the FortiLink VLAN on the Huawei switch, and we also configured DHCP discovery on the FortiSwitch:

config switch-controller global
set ac-discovery-type dhcp
set ac-dhcp-option-code 138
end

We also configured the trunk on the FortiSwitch:

config switch trunk
edit trunk1
set static-isl enable
set static-isl-auto-vlan enable
set members 51 52
next
end

The FortiGate discovers the FortiSwitch through FortiLink, but the switch is always displayed as Offline/Down.

FLP debug logs show that the FortiGate and FortiSwitch exchange packets successfully, and the physical link is UP.

Has anyone experienced this issue before when using FortiLink through a third-party core switch (Huawei)?
Any advice would be appreciated.

Thank you.