Hi @pepe058,
Doing a test on my own test site, the name Raúl ?aupari
is accepted when checking out:

Link to image: https://cld.wthms.co/VGGTbB
Let’s make sure this is not a theme or plugin conflict with WooCommerce, and please make sure that all plugins are updated.
First, backing up your live site before any testing and updates is highly recommended. If you would prefer not to do testing on your live site, first make a back up of your site, then create a staging site using this plugin WP Staging. This creates a copy of your live site where you can make tests without affecting your live site.
Temporarily switch your theme to one of our default – Storefront or Twenty Nineteen, then deactivate all plugins except for one – WooCommerce. If it shows correctly, then it’s a theme or plugin conflict. Reactivating each plugin one at a time, then see if the issue pops up again will tell us which plugin is conflicting.