Can make but not receive calls
I have recently been having a problem with Facetime on my Mac running OSX 10.8.5
I can make Facetime calls with no problem but when people try to call me it comes up on their device as either not available or it won't connect. Facetime opens on my Mac screen but just doesn't connect with the call, ie if just says 'connecting........' and nothing happens.
Most of the calls that come through to me are made with either an iphone or ipad running the latest updated OS.
Does anyone have any ideas why this might be happening.
Thank you.