CRM for Tablets & Phone Apps - Appointment not having Subject or Description Fields

Morning, we are currently on CRM online 2015 Roll up 1, and looking to use the Windows App.

However for some reason the two main fields we need in the appointment form 'Subject' and 'Description' do not appear when access the system via the APP.

Under field properties bit fields are selected as 'Available on Phone' under the Availability section in Display.

Any ideas on why this is not showing?

Thanks for your help

Graham