Why couldn't I declare Tsumo with this hand?
Riichi Mahjong has a one-yaku minimum before you can complete your hand.  While tsumo gives you a yaku if the hand is still closed, it won't give you anything if you've already opened your hand by calling melds.

For further details, you can read the related answer here: Why couldn't this hand win with ron?

Your hand, as it stands, doesn't have any yaku.  If the North wind was active (i.e. if you were playing in the North seat) you could earn a yaku by calling or drawing a third North tile, but then you would be stuck with a pair wait on one of the 2/3 character tiles.  Beyond that, about the only way you could win with that hand (short of hoping for a winning tile on the last draw or a kan draw) would be to swap out the characters and replace them with a set of dragons or an active wind.