I also had this issue until I realized you don’t just twist the knob

the collapse knob on the top that you're supposed to turn to fold up and store sometimes sticks or has possibly stopped working but its small

I feel like I'm going to break the knob when I try and turn it

I would have given this 5 stars, but the knob used to collapse the arms is extremely hard to turn.

This thing is supposed to fold up, there's a knob in the Center of the bars that says, twist to fold, but that sucker does not move and I have not been able to fold it up

The knob you turn seems difficult, but if you push down slightly as you turn, the assembly will collapse easily

you need to PUSH DOWN and twist the knob