Google Scholar: Citations appear on co-authors' accounts but not on mine
Since you mention in the comments that you edited the entry of the paper in your profile, what has probably happened is that Google Scholar now thinks that this is a separate paper, and does not link the citations from the original entry to the edited version. Unfortunately, this sometimes seems to happen when correcting certain fields in the entry created by Google Scholar.

A way to check and fix this would be to search for your paper under "Add articles", and checking if the same paper is listed there as not being in your profile. If so, you can add the original entry back to your profile and merge it with your updated entry. This should reintroduce the citation count, possibly with an asterisk next to it indicating that Google Scholar is not certain that both entries refer to the same paper.