Configuration Manager manifest synchronization failing since 8 July 2026 — endpoint returns 2-byte “OK” response

Question

Configuration Manager manifest synchronization failing since 8 July 2026 — endpoint returns 2-byte “OK” response

Rajh, Aleš 15

Has anyone else experienced Configuration Manager Updates and Servicing synchronization failures since 8 July 2026?

We have three independent Microsoft Configuration Manager hierarchies:

Test environment
Production T0 environment
Production T1 environment

All three started showing the same SMS_DMP_DOWNLOADER error during the last three days.

The affected request is sent to:

https://sccm.manage.microsoft.com/SCCMConnectedService.svc/Manifest

Configuration Manager builds a hierarchy-specific request containing the Tenant, Version, Ring, and Branch parameters. However, the endpoint now returns only:

OK

The resulting file is:

ConfigMgr.Update.Manifest.cab
Size: 2 bytes
Hex: 4F 4B
Content: OK

Because this is not a valid signed CAB file, dmpdownloader.log records:

manifest.cab (http response) size is 2
Error in verifying the trust of file '...\ConfigMgr.Update.Manifest.cab'
WARNING: Failed to call IsFileTrusted
WARNING: Failed to download and verify the manifest.cab

Rahul Jindal 11,721 Reputation points

2026-07-10T12:36:33.6766667+00:00

How are the Microsoft trusted root certificates looking in the environment? Are they still valid?
Rajh, Aleš 15 Reputation points

2026-07-10T13:27:19.1533333+00:00

Looks OK, certs are not a problem.

1 answer

Your answer

Rahul Jindal 11,721 Reputation points

2026-07-10T12:36:33.6766667+00:00

How are the Microsoft trusted root certificates looking in the environment? Are they still valid?
Rajh, Aleš 15 Reputation points

2026-07-10T13:27:19.1533333+00:00

Looks OK, certs are not a problem.

Answer 1

Ken Blevins 0

This started happening in my environment in all of my sites on the same date. This appears to be a Microsoft issue.

Rajh, Aleš 15 Reputation points

2026-07-10T13:20:29.45+00:00

Thanks. Im not alone.

An interesting detail is that the fwlink shown in dmpdownloader.log works:

Easysetup fwlink to download the manifest:

https://go.microsoft.com/fwlink/?LinkId=<masked>

When I download from this URL manually, I receive a valid 4.1 MB CAB file with a valid Microsoft digital signature.

However, the hierarchy-specific Connected Service URL:

Redirected to URL https:https://sccm.manage.microsoft.com/SCCMConnectedService.svc/Manifest?Tenant=<masked>&Version=<masked>&Ring=0;Branch=1

now returns only:

OK

DMPDownloader then saves this two-byte response as ConfigMgr.Update.Manifest.cab, which causes the subsequent signature-validation error.
Rajh, Aleš 15 Reputation points

2026-07-10T13:23:10.3333333+00:00

Thanks. Im not alone.

An interesting detail is that the fwlink shown in dmpdownloader.log works:

Easysetup fwlink to download the manifest:

https://go.microsoft.com/fwlink/?LinkId=<masked>

When I download from this URL manually, I receive a valid 4.1 MB CAB file with a valid Microsoft digital signature.

However, the hierarchy-specific Connected Service URL:

Redirected to URL https:https://sccm.manage.microsoft.com/SCCMConnectedService.svc/Manifest?Tenant=<masked>&Version=<masked>&Ring=0;Branch=1

now returns only:

OK

DMPDownloader then saves this two-byte response as ConfigMgr.Update.Manifest.cab, which causes the subsequent signature-validation error.
Ken Blevins 0 Reputation points

2026-07-10T13:59:40.2566667+00:00

Yes, I'm seeing the same behaviors with the URLs.