Black Rainbow

I'm trying to use the ISRU modules in combination with the aluminium hybrid rocket engine. I am amble to electrolyse alumina into aluminium and oxygen, but can't for the life of me figure out how to turn the oxygen into the liquid oxygen I need to power my engine. I'm trying to use the ISRU refrigerator (both the in-line and hex module), but to no avail: both ISRU windows only have options for atmospheric extraction and solar wind. The hex module, unlike the in-line version, gives me a slider for liquid oxygen <-> oxygen, and a button to activate the module, but it the status will still show "offline". I've read the relevant FAQ entry, and have placed external fuel ducts between all the relevant parts, but nothing is happening. The strange thing is that if I activate atmospheric extraction on the hex module, the conversion process continues to work even after I disable atmospheric extraction. It does not seem to matter if the module is activated or not, but I can use the slider to control the conversion (the in-line version does not have this slider when I launch the vessel). It stops working when I reverse the process and then run out of liquid oxygen to convert. I uploaded the craft file of the vessel I'm using to test the process. Am I doing something wrong, or is the refrigerator broken? EDIT: I can get it to work when I use the Universal Liquidficator, so I suspect something about the refrigerator is broken, or it is only meant for atmospheric use.