The error 0xC03F6601 typically appears in the Client-Licensing event logs when Windows or a Store app fails to validate a digital license. In most cases, "License Type: 1" refers to the core OS activation or a primary application subscription, such as an upgrade from Windows Pro to Windows Enterprise. Core Causes
Connectivity: Problems reaching the Windows Store API or organizational activation servers. Go to Settings → Update & Security →
Contact vendor support if:
Open Command Prompt as Administrator and run: Download the Microsoft Office Scrub Tool (o15-ctrremove
Connectivity Issues: The device cannot reach Microsoft’s Activation Servers or a corporate Key Management Service (KMS) host. or blocked by system policies.
If your system previously had a Volume License (KMS or MAK) installed—common in corporate environments or evaluation versions—and you attempt to install a standard Retail key without properly uninstalling the Volume License, the remnants of the old licensing ticket can conflict with the new one.
In simpler terms: Office tried to install your product key into Windows' secure vault, but Windows refused to accept it because the existing data is damaged, incorrect, or blocked by system policies.