No account preferences in Messages on iMac
iMac Messages no longer synchronises messages between iMac/ipad etc. Going to accounts in preferences in messages, the imessage account window is just grey.
Tried deleting ichat settings in Library/Preferences to no avail. Any suggestions?
IMAC (RETINA 5K, 27-INCH, MID 2015), OS X El Capitan (10.11.1)