A good Märzen should have a significant malt aroma, heavy on the Munich malt and accented by mild or moderate melanoidins or toasty notes from the decoction. You should have no hops, diacetyl, esters, or caramel (i.e., from too much crystal).
It's nearly impossible to get that malty richness from an extract batch, though, since you can't control your mash temperatures. "No nose," though, isn't necessarily a bad sign. Sometimes, it actually takes a little while for that maltiness to mature and come out. This is a beer that's meant to be lagered for some time, so give it that time.