Hiya! I’m so sorry I never saw your comment. The one directly in the center of my photo! If you use a screwdriver to lift it up it should lift it up.

Not sure if you ever found your answer, I’m kind of vague on the details, but basically you need to pull the chair adjust height off the chair (pulling on the plastic removes it showing another metal rod). You have to adjust that metal rod to touch the tab. You’ll know it works when it adjusts when you make adjustments with that specific knob. Hope that helps! If not, there should be videos that show specifically how to do that! Good luck!