How I can resolve the hreflang tag error?
International Targeting | Language > 'es-es' - no return tags
URLs for your site and alternate URLs in 'es-es' that do not have return tags.
5 Hreflang Tags with Errors
you need to have a 1-1 relationship between your pages and have return tags.
canonical to the ENGLISH page, alternate language ES-ES, and EN-US
canonical to the SPANISH page, alternate language ES-ES, and EN-US
so that Google will see that both "page-a-in-SPANISH" AND "/page-a-in-english" refer to each other
hope this helps you, good luck with that