How to use the prop-o-matic?

How do I use the prop-o-matic? I am playing a public prophunt map with my friend (not made by any of us) but I cannot disguise as a prop. When I look at something, it turns blue as if I can hide but when using the attack button it won’t let me. However, she seems to be able to hide. Why can’t I do it? Is there any setting I have to change?

I’ve tried multiple maps and I’m the party leader if that’s relevant

Dunno if you still have the problem, but if u go to Settings > Creative > Posses Prop and change it to left click it should work, its right above the LTM controls