Can't toggle handle mode on Asset Warp tool

I'm pretty new to animate, so not sure if this is a glitch or user error. I'm animating animal legs using asset warp tool. I created "bones" for each of the legs. The front legs are warping independently without affecting each other but I can't move one of the back legs without affecting/warping the other. I also can't toggle "handle mode" in the object settings, even with a joint selected. Is there another setting I need to turn on? Was it a drawing error? (Both of the back legs are separated in my drawing so I'm not sure why this would be the case). Thank you in advance for any help.