I'm thinking something is blocking one of the lines or ports. Try the whole assembly with no filters, membranes, or any guts... into a bucket.
1) If you do not get much water then you have a plugged port or passage way. You will have to find it by removing filter canisters one at a time, then bump the water on a second or two to see if each is getting water. Then when you find the right one use a pipe cleaner or something to unclog whatever port or line is clogged.
2) It you get plenty of water out into the bucket then back track and add one filter at a time starting with the settlement, micro, membrane and then DI.. (you get the order) ...see when the blockage occurs. Then replace that filter or put it back in the right direction....;) ....IF the RO membrane is messed up TRASH IT! do not try to use it... unless you want to kill your aquarium.