Have you told your web server (whatever it is; CentOS is an operating system, not a web server) to use the newly-issued certs? When you used the certonly command to certbot, that tells it to just obtain the certs--you need to configure your web server to use them appropriately.
Since you haven't even shared what web server you're using, I don't have a clue. I'd suggest you find that out, and once you do, try doing a web search for something like "configure SSL" and the name of your web server.
Looks like you got two separate certificates, but only configured one of them in your webserver.
You could also easily gotten a single cert for both hostnames.
Is there also a reason why you're using the standalone plugin? That's not very common nor useful if one has a working webserver running. Why not use the --apache plugin, or if you don't want Certbot updating any webserver configuration file, not the --webroot plugin?
I am pretty new in this stuff as I used to create SSL certs using Plesk with the old server and now I am not using Plesk anymore, so the standalone is the only way I new to create certs, which is pretty boring because I need to stop the apache server every time on a production server, so next time I will definitely try the apache plugin.
Is it better to have one certificate for both domains? Or one cert for each domain?
Anyway the issue seems to be solved now, probably a DNS propagation issue.