Cannot create distribution groups in OWA

Hi all,

Have just transitioned to Exchange 2013.  Users who use OWA now cannot create distribution groups.  They use IE11 on Windows 7 and are using the standard (not the light version) of OWA.

When in the 'People' pane of OWA there is only the option to add a new contact (as in screenshot below).  There is no option to add a group.  Desktop users of Outlook are fine.

Anyone else experienced this and found a solution?

thanks