When attempting to edit documents directly online double clicking does not appear to respond. Office files can be downloaded, edited and uploaded with changes however.
This is a known issue with the latest version of Office 2016 for the Mac on the current OS. OS-X Sierra is proported to fix this issue:
MyWorkDrive will continue to monitor this for Apple's fix. In addition we have edit online using Office 365 on our road map for release in Fall of 2016 as another option when editing office files directly online is needed.