I submitted a new version of the sitemap index for my site in Google Search Console two days ago. Soon after submission, GSC started saying that the index was "processed successfully", and yet has continued to display zero as the number of discovered URLs.
Note that my sitemap index points to about 11000 sitemaps, which provide actual links to pages.
I'm pretty sure the format of both the sitemap index and the individual sitemaps is correct.
Screenshot:
Should I worry about this? What does it mean?
Edit on 2020-02-03:
Google finally started displaying the right number in Total discovered URLs
. It must have happened sometime in January. Why so late - I have no idea...