we are experiencing a really difficult problem and TBH could do with a few ideas of things to check over.

So we have a high trust SharePoint application that works well however it just seems, most days to suddenly fall over and the connection between the application reports back 401 errors from the Webservice. Generally speaking seems to be roughly every 24 hours.

So just to clarify the responses have the information but are labelled 401

**HTTP/1.1 401 Unauthorized**
Cache-Control: private
Content-Type: application/json; charset=utf-8
Vary: Accept-Encoding
X-SharePointHealthScore: 0
SPClientServiceRequestDuration: 21
SPRequestGuid: 13d7b29f-b0f3-4007-b1da-0ddf83455225
request-id: 13d7b29f-b0f3-4007-b1da-0ddf83455225
X-AspNet-Version: 4.0.30319
x-ms-suspended-features: features=""
X-Powered-By: ASP.NET
WWW-Authenticate: Bearer realm="xxxxxxxxxxxx",client_id="xxxxxxxxxxxx",trusted_issuers="xxxxxxxxxxxxxxxxxx,xxxxxxxxxxxxxxxxx"
X-Content-Type-Options: nosniff
X-MS-InvokeApp: 1; RequireReadOnly
Date: Wed, 10 Mar 2021 08:32:51 GMT
Content-Length: 360

"_ObjectType_":"SP.User","_ObjectIdentity_":"xxxxxx:site:xxxxxx","Email":"[email protected]"


We have 3 IIS sites which have the app

  1. iis-a
  2. iis-b
  3. iis-c

2 SharePoint Frontends

  1. sp-a
  2. sp-b

There are basically 2 load balancers one for the 3 iis servers and 2 for the SharePoint frontends.

There are then a few backend SharePoint servers as well.

Temp solution

We have been doing an iisreset on the 2 frontends which does solve the problem and sometimes so does an a recycle of the security token service application pool and the default WebAppPool

Issue 2

Today we even had the really odd occurrence of everything being fine up until 8:27 and then fall over when the next user came along at 8:34.

So I think we are looking at a cache issue or something... maybe with the MaxConcurrentAPI (or something in that family) and perhaps with the load balancer.

Is there anything else, that we should be looking at?


Looking at our IIS logs, all the failed 401 have /subsite/_vti_bin/client.svc/ProcessQuery Why would that be, I've read some stuff about the Http Activation, but I'm not convinced. Can anyone clarify/hve a look at things we should be looking at.

  • are you using MFA in your tanent? If yes the use certificate for authentiating high trust software. Commented Mar 21, 2021 at 11:36
  • Don't think so it's just standard windows authentication Commented Mar 21, 2021 at 16:17

1 Answer 1


In the end we installed and reinstalled the HttpActivation in the farm and because we weren't using the windows load balancer (using a 3rd party one) we disabled the Request Management Service in sharepoint.

This seems to have resolved the issue...

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