At the time, around the 2010 period, there had been a couple of requests for the use of NATO AWACS, for example, for the 2010 Vancouver Olympics and in support of operations in Afghanistan. The NATO system was complex enough that it was not able to provide those capabilities when Canada asked, and so as a result of that, the view was that it wasn't a performing program from Canadians' perspective.
On March 1st, 2018. See this statement in context.