My husband and I have tested it with our iPads and we have both been able to face time each other from our respective devices. I tried a second time and, Hey Presto’, it worked. This time it told me to check my wi fi settings. The first time I got a different message from all the previous attempts. I put my Apple ID in for Home Sharing section, then went back to the Face Time settings and put my Apple ID into that section yet again. I went down settings on both iPads and discovered that the settings for Videos did not match. However, face time worked fine on my husband’s iPad.
I was not keen to fiddle with the DNS settings as I am no techie wizzard. I have just had the same problem as the others on this discussion.