Why does My Office 365 suddenly NOT see that I'm connected to the Internet? What Changed?

Office 365 apps must periodically reach Microsoft’s online services to verify the subscription and provide connected features. Even if the device is generally online, Office can show messages like the one in the screenshot when it cannot successfully connect to the required Microsoft 365 endpoints.

From the provided information, the most likely causes are:

1. Network connectivity or detection issues on Windows
   • Windows may not be correctly registering that the device has Internet access. Microsoft 365 activation and online features rely on this network connectivity status.
   • The documented guidance shows that when Network Connectivity Status Indicator (NCSI) does not detect Internet access correctly (for example, IPv4Connectivity shows NoTraffic or LocalNetwork), Microsoft 365 activation and online checks can fail even though the browser works.
2. Firewall or network changes
   • If a firewall or network device was recently reconfigured to block or restrict Microsoft 365 IP ranges or URLs, Office apps can lose connectivity to Microsoft 365 services while other general Internet access still works.
   • A previous change to Microsoft 365 IP ranges caused some customers’ firewalls to block the updated addresses, which led to loss of connectivity for Office apps until the allow list was corrected.
3. Subscription verification
   • Office needs to intermittently contact Microsoft’s servers to verify that the subscription is still active. If it cannot reach those servers for an extended period, it will report that it cannot verify or that Internet is required, and eventually may reduce functionality.

What likely changed is one of the following:

• Windows’ network connectivity detection (NCSI) stopped reporting Internet correctly, or its configuration was modified.
• A firewall, security product, or network configuration was updated and now blocks or filters Microsoft 365 endpoints.
• Office has not been able to reach Microsoft 365 subscription/activation services for some time, so it is prompting for Internet access.

To address this based on the documented guidance:

1. Confirm that Windows reports full Internet connectivity and that NCSI is working correctly (for example, by checking IPv4Connectivity and the HTTP probe URLs described in the activation network connection issues article).
2. If a firewall or network security device is in use, review recent changes and ensure Microsoft 365 IP ranges and endpoints are allowed.
3. Once connectivity to Microsoft 365 services is restored, retry the operation in Office so it can verify the subscription and resume normal behavior.

References:

• Microsoft 365 Apps activation network connection issues
• Internet connectivity issues in M365 apps after a change to the IP address range
• A subscription notice appears when I open a Microsoft 365 application