I think you need a certain amount of posts before you can give out rep, I'm unsure what that value is right now (it used to be around 100). I hope you refreshed the page to check if the rep changed because it won't change otherwise (at least not for me when using Chrome). Whoever gets repped can view who repped him and the reason in their User CP, however I don't think one can view to whom he has given rep in the past.