The problem was the diagram. It showed the vacuum latch already open with no clear explanation on how to open it. Then by playing around with it for another 15 minutes or so, by some fluke it opened. Soon after, we targeted in on it, and we figured it out! It's actually a very simple thing to do but hundreds of people are having the same problem with it. Moreover, none of the available YouTube videos show how to open and close this vacuum latch. But now there is a video tutorial to show you how it's done. In fact, it's the only one that does!
If this just described your dilemma then wait no longer. Jump to this YouTube video tutorial by ezreklama right now and finish up your yard work!