rear light.

first of all, sorry if i have posted this in the wrong area. one good reason is that i am desperate for some knowledge on this.
when it comes to tail lights, for me, small is beautiful. so the smallest one they had in the shop was for a crf.
No problem i thought. it looks exactly the same. One wire for earth or negative. One wire for the tail light and one for the brake light. Now when i activate the brake nothing. No illumination. anybody know anything about what can be done.
i know its a long shot. but i had to try.

Is the fuse okay? Plug in your old tail light and see it it works. signals may be on same fuse. If signals not working replace fuse.