My dissertation is linked to arXiv but its citations are not found in Google Scholar! My dissertation has been cited in a few good journals, which Google Scholar indexes. I have added my dissertation to Google Scholar and Google Scholar has even linked it to the arXiv version of my dissertation, which I have recently updated. The issue is that none of the citations of my dissertation have shown up in Google Scholar. What could be the cause?
Google Scholar, unfortunately, makes no particular guarantees about either timeliness or accuracy. I find that it is best understood as a byproduct of Google's business model, rather than a proper fully-supported tool.  

As such, it is not surprising that in my experience sometimes documents will take months, or even more than a year, in order to get properly sorted out by Google Scholar.

In the meantime, I would suggest to not worry about it too much: Google Scholar is not a definitive index, and should be used only to get a relative impression of the significance of a body of work, not to seriously evaluate bibliometrics.