Using HockeyDB's numbers here:
http://www.hockeydb.com/nhl-attendan...h.php?tmi=7328
I put together a list of all the Sens seasons, their attendance, their rank in the league in terms of attendance numbers and the result of the season.
92-93 10485 22/24 Missed Playoffs
93-94 10300 26/26 Missed Playoffs
94-95 9879 26/26 Missed Playoffs
95-96 13252 22/26 Missed Playoffs
96-97 15377 22/26 Quarterfinal
97-98 16750 12/26 Semifinal
98-99 17219 10/27 Quarterfinal
99-00 17508 9/28 Quarterfinal
00-01 17793 10/30 Quarterfinal
01-02 16919 15/30 Semifinal
02-03 17198 14/30 East Final
03-04 17758 13/30 Quarterfinal
05-06 19474 5/30 Semifinal
06-07 19372 5/30 SC Final
07-08 19821 3/30 Quarterfinal
08-09 18949 7/30 Missed Playoffs
09-10 18269 12/30 Quarterfinal
10-11 18378 11/30 Missed Playoffs
11-12 19356 6/30 Quarterfinal
12-13 19408 6/30 Semifinal
13-14 18109 14/30 Missed Playoffs
14-15 18247 16/30 Semifinal
15-16 18085 17/30 Missed Playoffs
16-17 16744 21/30 East Final
17-18 15228 26/31
Some key events that may have affected attendance and/or team spending(if you see anything I missed, feel free to let me know):
October 8, 1992 - Sens play their first game in the NHL at the Ottawa Civic Center(~10k capacity)
1993 - Rod Bryden becomes Chairman and Governor
January 17, 1996 - Sens play their first game at the Corel Center(now CTC)
02-03 - Owner Rod Bryden plagued with bankruptcy concerns
August 26, 2003 - Eugene Melnyk purchases the team and the arena
June 30, 2007 - Eugene Melnyk retires as Chairman and CEO of Biovail
December 1, 2010 - Eugene Melnyk starts divorce proceedings(Divorced with his wife shortly thereafter)
13-14 - Alfredsson signs with the Red Wings
Spring 2015 - Melnyk's liver transplant
December 2015 - LeBreton Flats proposals, including Rendez-Vous Lebreton's (RVL) Ice district type concept, revealed
February 24, 2016 - Phoenix Pay System goes live
November 2016 - RVL chosen as preferred bidder
Just looking at the attendance numbers, Ottawa is a fairly strong market and were in the top half of the league's attendance for 15 seasons straight. The past couple of seasons have been an anomaly since attendance numbers really haven't been this bad since the 96-97 season, and it really does coincide with the introduction of the Phoenix Pay System.
It doesn't help that the team has been really inconsistent for the better part of a decade now. Since the SC finals appearance, they've made the playoffs in consecutive years only once.