What am I doing wrong?

I just got the ACEBEAM TAC AA 2.0 which I've been really excited about, but when I fully click the talswitch and let go the light doesn't stay on, it flashes when the button is fully clicked in but then turns off. If I fully click and don't let go I can cycle through the modes but when I let go it turns back off, if I get to the mode I want by doing that and let go quickly and click again it just flashes and doesn't stay on? What I I missing? I thought you were supposed to be able to half click to cycle through modes and then fully click to select the mode you want, I also can't switch mode groups cause my halfclick fork off doesn't turn the light on and when I fully click after 20 the light doesn't stay on. I feel like I got a dud the the switch is messed up but mabey I'm doing something wrong?