Any of you guys use surefire tapeswitch on your weapon lights (I have an issue)

Brand new from Surefire bought a DS-SR07 tapeswitch. Old Click tailcap that came with the light functions fine. New one when screwed on is not functioning. Is there any sort of lock out feature built into these that I have not figured out?
I can not see a brand new one from Surefire being defective but anything is possible. Light is a M300V.
Picture is tapeswitch on left and original click cap on the right. Video is a short view of it working with one and not the other.

https://www.youtube.com/watch?v=qK-ykRQEdVg
http://img.photobucket.com/albums/v6...psidb7qlnx.jpg

I've heard some people complain that some of those endcaps aren't a perfect fit with all lights, and sometimes you really have to jam them on there to get a good contact...?

I didn't see anything obvious on your video, but that model is also supposed to have a "system disable" feature to prevent you from accidentally turning it on when you don't want to. Sometimes there's another on/off switch or you have to spin a knob or something. I think I've got one stashed on a gun in the safe - if you don't figure it out, I can try to go take a look and see.

Try pressing the button on the back only once, and then see if the tape switch works. Watching the video again, you might be doing enable, and then re-disable again and not realizing it, thinking you were going on/off.

Dumb ass award for me on this, as the problem turned out to be not screwing the tailcap completely down. The lock out feature on these is to rotate the tailcap a quarter to half turn counter clockwise from its normal position to lock out the switch. Tighten it down all the way and it worked like a champ. Now I just need to figure out if I prefer running it without a tape switch.