Ottawa strikes me as a difficult city from a N.A. pro-sports' perspective.
It's not tiny enough to be really 'small market', but it's much too small to be a safe territory for the NHL. 80% of the fanbase grew up as Leafs or Canadiens' fans and a lot of French-speakers in the region are from Hull and/or grew up Montreal fans. It's a really conservative (i.e., government staffed), fairly dull, milquetoast city, with nothing 'sexy' to attract big-name athletes. Plus it has Canadian winters, though not as bad as in Winnipeg or Edmonton (and arguably Montreal and Calgary).
That said, it's a Canadian market, so you'd think it would be easier. But hockey is expensive.
Everyone misses Quebec City in the NHL! Why not change the Sens to be 1/2 based in Ottawa and 1/2 based in Quebec City? In Ottawa, they'll be called the St. Lawrence Senators and in Quebec City they'll be called les sénateurs de st. Laurent.