I have paid for the certificate, completed all the psets in 2018 and completed the pset0 in January 2019.
Since you didn't complete everything in 2018, your completed work was carried over to 2019. However, some of the psets have changed and new material added. The requirement now is to complete all of the psets for 2019. So, you need to go back and look at your progress page for anything that is listed as not completed. This addresses completing the course.
However, I don't know how this plays with a paid certificate. Is there a deadline date for completing the certificate? If there is, and the date hasn't passed, then you should still be eligible.
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