We expected that volume and issue numbers would be included in the article metadata submitted to Crossref, but they are not. The issue metadata includes this information, as well as a publication date.
An example of an XML file is at http://users.cecs.anu.edu.au/~bdm/crossref-sample.xml.
It works for me (OJS 188.8.131.52):
Maybe the problem is you don’t have selected volume and number in the issue data.
The volume and issue numbers are specified there.
I hope the problem isn’t the checkboxes at the bottom, since they determine what is written the top of the table of contents of the issue and on the landing page of every article, which is quite a different function.
I believe that is exactly the problem. Please try with selected volume and number.
Thanks, you are quite correct. Frankly I think this is a bug, since we should be able to customize the appearance of our pages without breaking DOI submission.