Bro, I guess you hit the bars, as i also confused regarding the US sponsorship, VO thinks that you are not a genuine student you will leave canada or crossing borders :p I suggest you to dont show any supports from US :)
Is there is the Difference b/w Post Grad and Graduate Certificate ???
Because, one with Having a Bachelors(4 years) can apply in PG, but what for Graduate Certificate.. it will impact on visas u knw wht i mean