Using Zoho docs in China and in the US

Using Zoho docs in China and in the US

Hello-  My team is half in the USA and half in China.    We want to use Zoho docs for online editing.

My China team can access Zoho docs created by the USA team via links sent to them through e-mail or via Zoho CRM,(Link is uploaded as a project attachment)  but my China team can not edit the doc.   They have to first save the doc to their account then they can edit the doc, but the USA team can not see any of their edits.

All team members are co-owner collaborators on the documents they are sharing.

What are we doing wrong?  Why can't my China team and USA team see each other's edits.    The USA team can see edits of other USA team members.