I have asked you on MDL-73171, but I'll explain here too.
You have curled the URL locally on your development machine, but I suspect that it will not work on your server.
This host is using a LetsEncrypt certificate. The older LetsEncrypt root certificate expired in September 2021 and new certificates will use their new root certificate. Unfortunately that new certificate is not available in some places, including older versions of Debian, Ubuntu, MacOS, and some other locations. You can read about that expiry here: https://letsencrypt.org/docs/certificate-compatibility/
My hunch is that this curl of the URL will not work on your server because it has an out-dated root certificate and cannot verify the certificate chain. The error is correct and you have two options:
1) perform necessary updates to your server; or
2) disable certificate verification as Mark has suggested.