I keep having a problem trading in my Platinum GTS. I select a Pokemon to trade for, and when I try to select my Pokemon that matches what the other person is looking for, my Pokemon is not highlighted as matching the criteria. (Even though it does match.)

In Platinum the Pokemon lvl requested does not show
why? i don't know, but it's just plain stupid

So your problem is that your Pokemon isn't the level requested.

Ah-ha! Thanks!