is it a model you got from a seller / something bought used ??
on some psu you have some rear connector who need to be wired correctly for local use, voltage sensing etc ... sometimes they get removed and the psu is not working well unitl you make theses connection
happened on my Kepco, thats why i got it cheap
theses psu are advanced, you have powerfactor correction, power control with mosfets etc ... 3 spms sections etc ...
section 4 of the manual show this connector, at minimum you need to sense the output voltage
as a last resort like i would do is find all the datasheet parts and application notes, and try to figure out how it could work,
in this psu you have feedback lines who goes between the 3 main smps sections ....
and figuring out how they work may or will be a pain without trouble shooting manual from Xantrex ...