OP:
Two items from previous replies that you have not addressed:
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Exactly how did you install the DS3231 library? Directly in IDE using Library Manager? Downloaded as .zip file? If so, post (clickable) link to download page and let us know where you put the files on your computer.
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Did the library you installed include any examples? If so, did you look at them? If so, did any of them include arguments with the constructor for the DS3231 class?