When opening a .xlsm file with harmon.ie (v 5.3.0.9183) from SharePoint Online, a pop up showing eventID: 300 - "We're having trouble connecting to the server. If this keeps happening, contact your help desk." is thrown and the document remains stuck in "Read Only".
Opening the file directly from the online library through a browser (Chrome, IE11 tested) does not encounter the issue.
Nothing appearing in the Event log except the application 300 above. Events logged in the framework and harmonie .log files are:
harmonie.log - OCSAwarenessFactory - Failed to find ContactWrapper for sip
framework.log - !MESSAGE Failed to find ContactWrapper for sip
Any guidance on additional troubleshooting would be appreciated.