It could be a number of things:
How old is he? On the v3, the Matchmaker usually comes ages 7-8 rather than at the classic age of 6.
Have you paused him? If you pause your Tama, the growth process will probably get thrown off a little and events like marriage happen later.
Has the battery run out? When you reset and download, the Tama resumes at the last major event, like playing a game or waking up. This sets the time back and postpones other events like the Matchmaker.
You could also be missing it. The Matchmaker only appears on the screen for one minute at 10:30am, 3:00pm, and 7:00. Try setting your clock one minute before these times (10:29, 6:59 ect.) and wait to see what happens. Try all three times and if nothing happens at all, try again the next day.
Either way, the Matchmaker is guarenteed to come before your character turs into an oldie. Hope I helped.