Cannot sign in to FaceTime.

Lately i wasnt able to sign in to facetime. As soon as i sign in, i was taken to verification and when it was verifying it successfully verified then it stops there for about 5 seconds and takes me back to the sign in slide and it tells me that "My registering device does not have the appropriate credentials." I ve got a MacBook Mid 2010 Model with an Intel Core 2 Duo and 2 GB of RAM. With a 25 KB/s internet download speed. I am not sure what that is in Kbps. or Mbps.

Cheers!