Can not access files/attachments on Calendar in Mail App or add attachments to calendar via workdrive

Can not access files/attachments on Calendar in Mail App or add attachments to calendar via workdrive

Hi there, I have recently signed up for Zoho Workplace and am in the process of getting my events etc set up. 

When adding an event to the calendar on desktop, I select to attach a file and it does not give me the option to add the file from the workdrive - only directly from the computer which seems strange. When adding an attachment to an email I am given the option of selecting from the computer / workdrive or cloud. Why can I not access these options with the calendar?

Also and perhaps more importantly I have noticed that when I access an event on the calendar on the app on my iphone the files/attachments are not even there, neither is the Link/Url. 

I have looked through all the settings on the app and on the desktop and I cant see anywhere to change the settings to make the files appear. 

Please tell me where I am going wrong. 

Cheers