Unlike divorce which is where the Catholic Church says "A marriage existed, and now we are ending it," the annulment process says "From the very beginning, something was lacking that was necessary for this relationship to be called a marriage." Source: https://www.catholicnewsagency.com/resources/life-and-family/marriage/catholic-marriage-and-annulments
The annulment of a Catholic marriage can be permitted where “A marriage where one party cannot have children and they did not inform their partner about this.” Source: http://www.catholicforum.com/forums/showthread.php?58108-Acceptable-Reasons-for-Annulment-of-a-Catholic-Marriage
Therefore, if it is discovered at some point after the marriage that one or the other is infertile, but that was not known prior to the marriage, then it would not be grounds for an annulment. Various Catholic sources deal with infertility and medical treatments that are available.
Edit: For clarity, that means infertility is NOT grounds for an annulment, UNLESS the infertile person knowingly concealed that fact prior to the marriage taking place. In the situation described in this question, there is an assumption "that no fraud was committed and the person didn't know they were infertile." Conclusion - no grounds for an annulment.
Thanks to JBH who pointed out: "Infertility isn't grounds for annullment - period. Deceit and fraud are, likely no matter the subject."
Here is a link to an article on how the Catholic Church views the annulment of a marriage: https://en.wikipedia.org/wiki/Declaration_of_nullity