Hola Mercedes,
There is a chance that this is related to a known issue with translations for fixtures (default terms and taxonomies etc in AtoM) when upgrading - we currently have no way of applying new fixture translations to upgraded sites, so that could be why the Genre taxonomy is missing a Spanish taxonomy name in your version. There may still be a way we can help, but I'd like to rule out some simpler possibilities first.
Let's try a few basic things and see if it helps.
First, if you are using your AtoM site in Spanish, make sure you navigate to Admin > Settings > i18n languages and confirm that Spanish has been added as a language there.
Next, let's try regenerating the slugs:
Then reindex your site:
Remember to test in an incognito or private browser, or else clear your browser cache first! Let us know how it goes!
If it doesn't work, please do let us know more about your installation environment, as I asked in your other thread.
Cheers,