AR1220EVW PoE

<Huawei> system-view
[Huawei] interface ethernet 0/0/4
[Huawei-Ethernet0/0/4] poe legacy enable

The poe legacy enable command enables the power sourcing equipment (PSE) to check the compatibility of the power device (PD).

This post was last edited by StarOfWest at 2018-05-31 02:10. try to increase the priority - critical is the highest.
<Huawei> system-view
[Huawei] interface ethernet 0/0/6
[Huawei-Ethernet0/0/6] poe priority critical
Warning: This operation may power off some PD with lower priority.Continue?[Y/N]:y

Try to disable or enable poe legacy. Currently I see it's enabled on the port, so 802.3af or 802.3at standards compatibility is enabled. try to disable it and test again.
<Huawei> system-view
[Huawei] interface ethernet 0/0/6
[Huawei-Ethernet0/0/6] undo poe legacy enable

Try to test with another Huawei device, maybe a POE LAN switch like S5700, if it's working, you can compare the configuration on both sides and see the differences.

Anyway I recommend to get in touch with TAC, this is more like their type of case, maybe they meet this kind of situation before with Cambium and EnGenius devices.

http://e.huawei.com/en/service-hotline-query
Cheers!

Do you have the POE power supply for the router?

I've standard power supply.
Do the PoE functionality require second power supply ?

Yes, for PoE you need the external power supply.

very good!