You wouldn't get a credit from Kobo for eligible transferred Sony books. Sony "credits" are being issued as a check just like they were for the first round of things in 2014. Hopefully you're still at the same address Sony had on file for you when they had a store or you updated your info with the settlement administrators so you get your check if you had eligible books.
Eligible books are those from and purchased between April 1, 2010 and May 21, 2012 published by Hachette, HarperCollins, Simon & Schuster, Penguin or Macmillan.
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As to getting Kobo to transfer your Sony books at this late date I'd guess chances are little to none.