Again. You did NOTHING wrong. You can’t cause this problem, and you can’t fix this problem. Your hoster broke your server, you need to ask him to fix it.
Some technical details, that you can use to understand it better.
Plugin calls the php function from the php libcurl library and asks that function to connect to facebook.com
php libcurl passes that request to the Linux system library called cURL
cURL tries to connect to facebook.com using some Linux core libraries for http and tcp/ip
Somewhere between cURL and Linux core libraries call to facebook.com goes to the DNS resolver and asks it for the IP of the facebook.com. DNS resolver should return the IP that could be used for the actual connect. On your server DNS resolver returns IPv6, but either cURL or Linux core libraries are not configured to use IPv6
You need to contact your hosting provider and either configure cURL and/or Linux core libraries to work with IPv6 or reconfigure DNS resolver to return IPv4.
You never had it before, because your server wasn’t broken before. Somebody messed it up.