"Unknown error trying to lock file." SharePoint Online

Greetings,

I am setting up a document library that will be used by users in our terminal session environment.  Hosts are Windows 2008 Server R2. We are setup in a Office 365 / SharePoint Online. We have Office 2013 installed on the hosts.The test user that I have setup has Edit permissions to this document library. Whenever the user goes to open a document in the library it always opens in "Read Only" mode, and when trying to edit I receive the message "Unknown error trying to lock file." I have read other threads and already changed the following.

-Put our SharePoint in the correct internet zone / and trusted sites (GP)

-Setting to require documents to be checked out before they can be edited (Library Settings)

-Allow documents for opening in Read/Write (GP)

-Added registry entry for AuthForwardServerList including our Sharepoint site (Registry)

Any help would be greatly appreciated.

Thanks,

-Magoo