My inlaws have just switched over to TalkTalk, having the same issue.
Can't get to Facebook via their WiFi.
Unfortunately I'm too far away to help but after seeing this is a known issue, asked them to contact TalkTalk.
You can imagine the response haha... "Since you can get to all other sites, it is not a TalkTalk issue, please contact Facebook instead".
Of course they turn off WiFi and use 3G and then Facebook works just fine.
same, my wifi seemed to just not load Facebook and Instagram the last few days. please can someone help