Experiencing authentication failures on NPS Server after installing KB5055661 on My Active Directory.

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Experiencing authentication failures on NPS Server after installing KB5055661 on My Active Directory.

Amin Najafi 0

i install KB5055661 on widnows server 2016 active directory but i got error of authentication failed due to user credential missmath on my nps, is that relate to this KB? any upgrade or issue for this Kb can you find?
MY ADDS : win2016
MY NPS: win2019

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Answer 1

Joseph Tran 4,080 Independent Advisor

Installing KB5055661 on your Windows Server 2016 AD shouldn’t directly break NPS authentication. That update is just a servicing stack update and doesn’t touch authentication.

However, sometimes updates can indirectly cause issues, especially around certificates or AD mappings. Since your NPS is on 2019, it’s worth checking:

Certificates are correctly mapped to machine accounts.
NPS policies and settings aren’t misconfigured.
Event logs on both AD and NPS for errors.
Test with different clients to see if it’s widespread.

Also, KB5055661 has been superseded by newer updates, so staying fully patched can help avoid quirks.

Amin Najafi 0 Reputation points

2025-10-04T04:36:57.1233333+00:00

Dear Joseph, thank you for your reply. I have updated my Domain Controller (DC) and NPS, and I even attempted a full upgrade to DC 2022. Despite this, I continue to receive a mismatch error in multiple locations. All of our NPS and DC servers are up to date
Joseph Tran 4,080 Reputation points Independent Advisor

2025-10-04T16:20:47.4+00:00

Since both your DCs and NPS servers are fully patched and even after upgrading to Server 2022 you’re still getting credential mismatch errors, this is likely not update-related anymore.

At this stage, I’d focus on a few possible causes:

Certificate mismatch: Check if your NPS servers and DCs are using the same trusted root CA and if the client authentication certificates are still valid and mapped correctly in AD.

Time sync issues: Even a small clock drift between DCs, NPS, or clients can cause authentication failures.

Duplicate SPNs or stale machine accounts: Run setspn -X to look for duplicates and make sure the NPS servers’ computer objects are healthy.

Kerberos token or channel binding issues: Try enabling Schannel logging or temporarily disabling “Network Policy Server certificate revocation check” to test.

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Experiencing authentication failures on NPS Server after installing KB5055661 on My Active Directory.

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