Axigen connector: Outlook 2016 calendar entries don't sync with server until restart

When using axigen connector, if a calendar entry is added into Outlook 2016 it goes into an ‘unknown folder’ and doesn’t sync with the server. As per photo.

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When restarting outlook, for some reason this is then sync’d with the server.

Why do I need to restart Outlook for this to occur? I understand that I can use CalDav etc, but I want to use the connector as this is it’s primary purpose.