Update: Microsoft have since released a fix for this issue.
After a Windows 7 update released on 08/01/2019, the smb connection from the GMG PC to any connected systems (e.g. Macs) stopped working. This means you can no longer connect to your shared hotfolders.
The update affected is "Security Update for Microsoft Windows (KB4480970)".
To resolve the issue, please uninstall the update from Control Panel > Programs and Features > View Installed Updates:
Once uninstalled and restarted, the smb connection should be working again. We recommend to disable Windows Updates until the issue is resolved.