Microsoft Office 2016 Licensed via KMS but with Activation Splash Screen on launch

Resolved by following https://support.office.com/en-us/article/Office-repeatedly-prompts-you-to-activate-on-a-new-PC-a9a6b05f-f6ce-4d1f-8d49-eb5007b64ba1

• Close the activation window and all Office apps.
• Right-click the Start button on the lower-left corner of your screen, and select Run.
• Type regedit, and then press Enter. Select Yes when prompted to open the Registry Editor.
• On the left side of the Registry Editor, under Computer, navigate to the following key in the registry: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\16.0\Common\OEM
• Right click the OEM value and click File>Export.
• Save the key.
• After the key is backed up, select Edit>Delete.
• Repeat steps 3-6 for the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\16.0\Common\OEM
• Close the Registry Editor and start Office again.