So, this is no bueno. But, yet you applied for a PR under the Common-Law program of the Family class. I have an opinion, but you might want to double check with an immigration lawyer (a proper lawyer -- not consultant), or your local MP.I had SA & AIP in Jun. 2017 and totay a letter from IRCC was sent to my common law sponsor's email, please help!
My common law girlfriend was previously granted PR under her parents' family application.
I discussed with my girlfriend why she stated "single" on her landing on 23 August 2013, and she said she did not even understand the clear idea of "common law" at that time because in our country we usually use "single" or "married". We do have been living together since 2011 but we never bothered to clearly check the right definition of marital status of us at that time......
Any suggestions are appreciated!
You've submitted evidence, I am assuming, of co-habitation from 2011 forward. If that's the case, then your girlfriend has misrepresented herself to CIC at the time they sought to grant PR status for her. They are demanding a letter explaining what happened.
So, I would write exactly what you have stated here, and submit that to CIC, and hope that they won't do much more than finger-wagging over not reading the rules when applying. With your letter, it would probably help to have government forms from her Country of Origin, that you can show that only state "single" or "married".