The flow restrictor will be in the yellow waste water line. It should be in the line close to the flush valve. You should find a place where the line has a "joint". This is where the capillary restrictor is located. You'll have to pull the line apart and then pull the restrictor out. If the restrictor has a tube attached (tail), that end goes towards the drain. If it doesn't, the long end (below the flange) goes to the drain, and the short end towards the RO housing. Water flow in a 24 GPD system is only 1 gallon per hour... max. There will be very little flow, even when it's at peak performance. This doesn't explain not flowing at all. If it works with the RO membrane removed, make sure you are installing it in the correct position. The end with double O-rings goes in first, and the rubber skirt-type seal goes towards the cap side of the housing. Also make sure everything is connected in the right order and in the correct ports. Water source line to "in" port on sediment cartridge, "out" port on sediment cartridge to "in" port on charcoal cartridge, "out" port of charcoal cartridge to the port on the cap of RO housing, the "center" port on end of RO housing to "in" port on DI cartridge. Again, the port on the edge of RO housing goes to your flush and restrictor valves.