Why are some issues missing for CrossRef XML export?

In order to correct some important metadata errors on CrossRef, I’ve been exporting XML files for issues of certain of our journals using OJS 2.4.6. For one journal, with 24 issues, I’ve successfully updated the metadata for all but a few using this method. The missing issues simply don’t show up on the register/export issue page in the CrossRef Export/Registration plugin. From this screenshot, you can see that the issue for Volume 13 (2003), for example, has been published (and in fact has DOIs successfully assigned to all articles) but isn’t available for exporting the XML file with the metadata that needs to be updated. I’m stumped.

To be listed for export, an Issue must have one or more published articles which have both a DOI and a published date.

Can you confirm this is the case for the articles within the issues in question? Do these articles show in the list of “All Articles” within the plugin?

Thanks for pointing out this code. I can confirm that the articles in the issues in question show up under All Articles in the plugin and have a DOI and a publication date. So, I found a solution to my problem, without however achieving an understanding of why the issues don’t show up under All Issues. Under All Articles, the articles are sorted by publication date. So, it was easy to select just the ones from the issues I wanted the metadata for and then hit Export at the bottom.

Another reason the Issue will not display in the list is if all articles within the issue have already been registered. In your case, if you were making metadata corrections, I suspect this was the case: