Replacing a failed device with a replacement device may require an upgrade of the SGOS version to match the version on the failed device, if this is the case it is critical the correct upgrade path be followed as outline in the "SGOS Upgrade/Downgrade Guide (5.x and 6.x)" documentation, see below for link.
RMAed devices typically come with older versions of SGOS, in this particular case the device, a SG810-5, had a 5.4 version of SGOS installed. Once the customer had followed the correct upgrade path to get the device onto 6.2 they where able to license the device correctly.