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2nd SMA rapid shutdown that is not working for me

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    2nd SMA rapid shutdown that is not working for me

    Greetings all this is the second time I have gone out to a site to replace an inverter and am unsuccessful at getting a rapid shutdown to shut the DC off.
    My understanding is the rapid shutdown acts as a DC PV disconnect? You just hit the button and the system opens a contactor?
    When I did that the LED still glows red and I measure 480VDC at the inverter.
    Part numbers are SMA RSB-2S-US-10 and RSC-1X-US-10
    Anyone have any tips or experience with these on here?
    I notices in the manual it says:
    8 Checking the Function of the Rapid Shutdown System
    The Rapid Shutdown System is supplied via the PV array. If there is insufficient irradiation on the PV
    array, the supply voltage of the Rapid Shutdown System is too low and the function of the Rapid
    Shutdown System is not able to be checked.
    • The Rapid Shutdown System must be commissioned.
    • Wait a minimum of 60 seconds from powering on the system before testing the Rapid
    Shutdown System functionality.
    There must be sufficient irradiation on the PV array.
    So does this thing not work if there is not enough sun? It was pretty early AM when we got there and cloudy.
    There is of course a 'DC disconnect' however its part of the inverter being replaced.
    Thanks in advance.
    Comments based on 2017 NEC unless otherwise noted.

    I only did one of these once, but if I recall, you wouldn't see the red LED if there weren't enough array voltage to operate. In other words, it's malfunctioning. I could be wrong but I believe it is supposed to work even if it is too dark to check that it worked. I.e. once the sun comes up it will respond to the push button.