certificat expired

What version of WordPress and PHP are you using?
You might need to update your PHP to 5.6 or later.

That issue is due to an expired certificate on your server. If you don’t have access to manage that, please speak with your webhost and tell them that this — https://letsencrypt.org/docs/dst-root-ca-x3-expiration-september-2021/ — is impacting you.