Hi Francesco,
Thanks for getting in touch with us.
Please note that just because you have alt in media doesn’t mean it is showing up on the actual website. Without going into more detail, I would recommend checking the page source of your homepage and check the page source.
Look for the filename that Rank Math says is missing alt and check if there is really an alt text attached to it. If not, please check with your theme provider. If you see that particular image already has alt, please share the URL so we can check in more detail.
Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.

as you can see the ALT variable for the image is defined. Please can you help me to solve it
We might need to take a closer look at the settings. Please edit the first post on this ticket and include your WP logins in the designated Sensitive Data section.

It is completely secure and only our support staff has access to that section. If you want, you can use the below plugin to generate a temporary login URL to your website and share that with us instead:
https://wordpress.org/plugins/temporary-login-without-password/
You can use the above plugin in conjunction with the WP Security Audit Log to monitor what changes our staff might make on your website (if any):
https://wordpress.org/plugins/wp-security-audit-log/
We really look forward to helping you.
Hello,
I have updated the sensitive data as requested. Can you please check further?
Thank you.
Hello,
Thank you for contacting Rank Math today.
Rank Math is currently not fully compatible with the Divi page builder and it is unable to analyse the ALT tags added via the image module.
Please note that the failed score is only used to serve as a benchmark and it will not affect your SEO.
Looking forward to helping you. Thank you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.