Activation on Macbook Air 13

Running OS X El Capitan (10.11.3) on a Macbook Air 13". 1.6 GHz processor, 4GB memory, 259 GB storage.

Recently bought this Macbook (new) and did a manual migration from an 11" Air.

Not able to activate FaceTime on this device.

Have checked date and time, restarted mac and confirmed I'm using the correct apple ID and password. Don't have 2 step verification enabled.

The 'FaceTime\preferences' menu is greyed out so I'm not able to select it.

When I submit my password and ID it thinks about it for a while and then I get the following error message.

Error message "an error occurred during authentication".

I'm running it successfully on an iPhone and an iMac.

Would welcome any further advice.

Thanks