How to solve error: Missing return tags hreflang in multilanguage website

Question

I have a multilanguage website, which has the following properties:

1. It does not have a .com/ page, it always usex suffixes for every language, i.e. example.com/es, example.com/en, etc.
2. I have configured <link rel="alternate" hreflang="es" href="http://www.example.com/es" /> for every language.
3. I am using also <link rel="alternate" hreflang="x-default" href="http://www.example.com" /> as recommended by Google ( see here )

However, I am still getting the error. I don't know if it is due to not having a example.com/ page, because the user is always re-directed to the suffixed version, based on the browser default language.

Solution

If page A links to pages B and C, page B should also link to pages A and C, and page C should link to pages A and B. In addition, each page must link to itself.

So that means all pages will have the exact same hreflang markup. This page has more info: https://hreflang.org/missing-return-tags-error-for-hreflang/