Adjustment of Status - I-485

(Florida, Oakland park), Had our interview on the 8th of January 2019, after filling for the I-485 since March, 2017.The IO took so much time interviewing us; asking series of questions which we both answered correctly as much as we could. . .She later gave us a letter saying our case has to be reviewed.
I just received a mail in the post today- 26th February requesting to submit proof that my previous marriage was legally ended-(such as a final absolute divorce decree; that was registered by the government agency authorized to register such documents). . .I did submit this(divorce certificate) along with my application initially and the IO asked for same during our interview which I also gave to her that she made a copy.
How do I address this situation? My ex- wife filed for the divorce and the copy of the judgement i.e the divorce petition/decree of dissolution of marriage is what I have. Anyone knows how to go about this? I'm from Nigeria.
Thanks guys!