2 problems, most lights like this are designed to be accessed from the head (FW3A). The second problem is when you unscrewed it like this there is a brass retainer piece that is stuck up inside the cap now that keeps everything in place when the very tail cap is removed. This is what the tail clip rides on.
So to reassemble I would separate the brass spacer from the very tail cap then the following.
Washer, Switch, plastic spacer with the longer parts facing the switch, Rubber boot on the top of the flat then the brass locking nut. I use tweezers or piece of metal bar to lock this in place. The chrome button assembly is pretty self explanatory when you get it apart.
I have taken apart and reassembled upwards of probably 50 of these so if you need help let me know or join the Reylight Facebook group for more help.