Hi and welcome to the forum! Open Graph won’t work on other websites (like Facebook) because of this security system:
Since you have a custom domain, you can configure Cloudflare on your website to bypass the security system and for Open Graph tags to show up on other websites.
There’s no need in disabling the old cert ---- The old cert become inactive as soon as your new cert was installed and active. That is, you can have multiple certs while install one only.
Add on to @Frank419 , it is actually recommend to have an SSL Certificate installed on InfinityFree to ensure secure communication between Cloudflare and InfinityFree
You’ll have to enable the Cloudflare proxy on the DNS records that serve the website (so change the grey cloud to orange on @ and www), then set the SSL option to “Full” always on the Cloudflare dashboard for your domain. But for now seems like the IP your website is on is down for me, so this change will work when the server will be back online.