Make sure your chamber is clean and dry, that there is no ice in it, and that the drain valve is closed. Make sure the pump is installed on the right side of the machine, and that the drain valve is on the left.
Check that no residual water is inside the chamber or drain hose. When attempting to pull vacuum, this water will evaporate and prevent the pressure from dropping.
Go to settings, then manual hardware control, and turn on the vacuum pump and the refrigeration together. This test will determine what ultimate vacuum pressure the unit can reach. After running for an hour, the unit should be able to reach below 500 mtorr.
Check that the door is sealing properly. The door seal should create a solid ring most of the way around the door seal about 1/8" thick without vacuum. While under vacuum the black seal should be 1/2" thick all the way around. You may need to clean the black seal as well. If there is any hair, fur, or any other contaminates in or on the seal it could be causing the vacuum error.
If the door seal has large gaps in the seal while not under vacuum, try turning on the vacuum and pushing on the door. If the door starts to seal only after pushing on the door, then the door needs to be adjusted so there are less gaps around the door. Sometimes the doors shift in transit and can cause this issue. You can also make sure that the door handle is completely closed. This will have a similar affect.
Cold food added to a warm chamber or warm tray will cause ice to melt in the food. This melting can lead to a vacuum error as well as excess water being ingested by the pump. To prevent this from happening, simply start the cycle for 30 minutes prior to putting food in the chamber. This will ensure that cold food is being placed into a cold chamber.
Check that the drain valve is closed. If air is escaping through any gaps between the hose and drain valve, then remove the drain valve from the hose, cut the hose back by 1in (25mm), and reinsert the hose. The drain valve itself might have a leak (sometimes a small puncture in the hose will also cause a leak). Drain valves can be purchased through our website. If a hose has a cut in it replacement hoses can also be ordered from our website.
Check that the vacuum pump oil is clean. Water and other contaminants will discolor the oil, and will cause the pump to not operate as efficiently as possible. Too much oil will also cause the pump to not draw vacuum as efficiently.
If the chamber is able to achieve pressure when testing using manual hardware control, but is not able to achieve pressure when running a recipe, make sure the food is fully frozen and that the recipe has plenty of time on the freeze cycle.