Two PSUs included in i4600 box, problem happens with PSU2

Hi all, We have two boxes i4600, which are included 02 PSUs in each device. But the PSU2 have problem when show by command:

Appliance Power Supply Status

Index  Status  Current

1      up      AC

2      down    NA

No log alert, although we have use enable command:

sys db platform.powersupplymonitor {
   value "enable"
}

Here is LED status:

front LED status

end LED status

Anybody had the same issue? Please help us. Thank you so much.