Recently I got the error message, No network connection available, operation cancelled, when I try to add a Facebook sharing account. The problem is with the curl library. We need to update it the to latest version. Add extras-devel, extras-testing repository if you cannot find the library in the stable channel.

Open terminal (Ctrl + Shift + X) and give the following commands:

root # change to root user
apt-get install libcurl3

Now re-validate your Facebook account from the sharing accounts.