MICROSOFT has issued a service advisory warning that Always On VPN may fail on some Windows 11 devices after the September 2026 update. The issue affects configurations using automatic protocol selection, where the VPN switches between IKEv2 and SSTP when a connection attempt fails. Affected connections can remain stuck on “Connecting”, repeatedly retry, and eventually report that the specified port is already in use. The problem can prevent enterprise users from accessing corporate networks and related internal services.
Microsoft’s investigation found that connection resources may not be released correctly when the automatic protocol switch and subsequent retry occur, leaving the port unavailable. The company’s temporary workaround is for IT administrators to replace automatic protocol selection with a fixed IKEv2 or SSTP configuration, chosen according to the organisation’s network and security requirements.
Administrators should first verify that the VPN gateway, certificate authentication, multi-factor authentication and client policies support the selected protocol. The report does not state that Microsoft has released a permanent fix.