Hello @edu_horse
For social icon of the network Xing to be displayed you need to add custom CSS.
To add custom CSS you need to go to Admin Panel / Appearance / Customize / Theme Options / Advanced Options.
Here you need to copy and paste below CSS.
.education_hub_widget_social ul li a[href*="xing.com"]:before {
content: "\f168";
}
.education_hub_widget_social ul li a[href*="xing.com"]:hover {
background-color: #006464;
}
Hope this will help to resolve your issue.
Let us know how it goes.
Regards!!!