Air Canada Altitude 90 day challenge.
And also I learned that if you've had AC Status before, you're not eligible for Status challenge.. I emailed the email above and here's their response:
Hello,
The status challenge is for customers that hold a top tier status with other airlines and have never held an Altitude status with Air Canada. Seeing that Mr. whatchamackallit03 was Prestige 25K in 2015, he is not eligible for the Status Challenge.
Best Regards,
The Air Canada Altitude Team