English Translation
There were not many present.
There were not many present (people there). is not the same as
There were not many presents (gifts).
Which is a correct translation?
In this case, I’d tend to say that “présents” is the correct translation; if it was talking about gifts, the plural would be used, I think. Whereas with people it seems to be invariable (see oxford’s dictionary, second meaning: “There were 200 people present at the meeting.”).
Although the sentence seems a bit clunky. I think I would have said something like “Many were not present”