SCCM 1810 Task sequence / HTTP connection issue

[GDCMike]

Hello!

I'm very much an SCCM noob, and I'm trying to diagnose a problem - the main symptom being that the Config manager client step of the TS fails to install, with the following errors in the log file:

Locations: Multicast = 0, HTTP = 1, SMB = 0.	
Package Flags: 0x00800000	
Multicast is not enabled for the package.	
Trying ://xxxSCCM-02-xxx.xxx.LOCAL/SMS_DP_SMSPKG$/xxx00002.	
GetDirectoryListing() entered	
Initializing HTTP transport.	
Setting URL = ://xxxSCCM-02-xxx.xxx.LOCAL/SMS_DP_SMSPKG$/xxx00002.	
   Address=[URL unfurl="true"]http://xxx-SCCM-02-xxx.xxx.LOCAL,[/URL] Scheme=http, Object=/SMS_DP_SMSPKG$/xxx00002, Port=80.	
WinHttp credentials set	
CLibSMSMessageWinHttpTransport::Send: WinHttpOpenRequest - URL: xxx-SCCM-02-xxx.xxx.LOCAL:80  PROPFIND /SMS_DP_SMSPKG$/xxx00002	
Not in SSL	
Error. Status code 500 returned	
dwHttpResultCode >= 200 && dwHttpResultCode <= 299, HRESULT=801901f4 (..\downloadcontent.cpp,952)	
Http result: 500	
SendResourceRequest() failed. 801901f4	
SendResourceRequest(pCertContext), HRESULT=801901f4 (..\downloadcontent.cpp,612)	
oDavRequest.GetDirectoryListing (setDirs, setFiles, pCertContext), HRESULT=801901f4 (..\resolvesource.cpp,3301)	
Download() failed. 801901f4.	
Trying ://xxxSCCM-02-xxx.xxx.LOCAL/SMS_DP_SMSPKG$/xxx00002.	
GetDirectoryListing() entered	
Initializing HTTP transport.	
Setting URL = ://xxxSCCM-02-xxx.xxx.LOCAL/SMS_DP_SMSPKG$/xxx00002.	
   Address=[URL unfurl="true"]http://xxx-SCCM-02-xxx.xxx.LOCAL,[/URL] Scheme=http, Object=/SMS_DP_SMSPKG$/xxx00002, Port=80.	
WinHttp credentials set	
CLibSMSMessageWinHttpTransport::Send: WinHttpOpenRequest - URL: xxx-SCCM-02-xxx.xxx.LOCAL:80  PROPFIND /SMS_DP_SMSPKG$/xxx00002	
Not in SSL	
Error. Status code 404 returned	
dwHttpResultCode >= 200 && dwHttpResultCode <= 299, HRESULT=80190194 (..\downloadcontent.cpp,952)	
Http result: 404	
SendResourceRequest() failed. 80190194	
SendResourceRequest(pCertContext), HRESULT=80190194 (..\downloadcontent.cpp,612)	
oDavRequest.GetDirectoryListing (setDirs, setFiles, pCertContext), HRESULT=80190194 (..\resolvesource.cpp,3301)	
Download() failed. 80190194.	
Trying ://xxxSCCM-02-xxx.xxx.LOCAL/SMS_DP_SMSPKG$/xxx00002.	
GetDirectoryListing() entered	
Initializing HTTP transport.	
Setting URL = ://xxxSCCM-02-xxx.xxx.LOCAL/SMS_DP_SMSPKG$/xxx00002.	
   Address=[URL unfurl="true"]http://xxx-SCCM-02-xxx.xxx.LOCAL,[/URL] Scheme=http, Object=/SMS_DP_SMSPKG$/xxx00002, Port=80.	
WinHttp credentials set	
CLibSMSMessageWinHttpTransport::Send: WinHttpOpenRequest - URL: xxx-SCCM-02-xxx.xxx.LOCAL:80  PROPFIND /SMS_DP_SMSPKG$/xxx00002	
Not in SSL	
Error. Status code 404 returned	
dwHttpResultCode >= 200 && dwHttpResultCode <= 299, HRESULT=80190194 (..\downloadcontent.cpp,952)	
Http result: 404	
SendResourceRequest() failed. 80190194	
SendResourceRequest(pCertContext), HRESULT=80190194 (..\downloadcontent.cpp,612)	
oDavRequest.GetDirectoryListing (setDirs, setFiles, pCertContext), HRESULT=80190194 (..\resolvesource.cpp,3301)	
Download() failed. 80190194.	
DownloadContentAndVerifyHash() failed. 80070002.	
DownloadContentAndVerifyHash ( pszPackageID, L"SMSPackage", saHttpContentSources, saSMBContentSources, saMulticastContentSources, sDestination, dwFlags, L"", 0, dwPackageFlags, mapNetworkAccess ), HRESULT=80070002 (..\resolvesource.cpp,3863)	
DownloadContentLocally (pszSource, sSourceDirectory, dwFlags, hUserToken, mapNetworkAccess), HRESULT=80070002 (..\resolvesource.cpp,4090)	
TS::Utility::ResolveSource(sClientPackageID, sClientPackagePath), HRESULT=80070002 (..\basesetuphook.cpp,1746)	
Failed to resolve package source "xxx00002"

Other packages have this:

Locations: Multicast = 0, HTTP = 1, SMB = 1.

So, they fail to connect via HTTP, but connect via SMB eventually.

My thoughts are that this is some sort of authentication issue, as if you try to browse to the address from the server itself you get:

HTTP Error 500.19 - Internal Server Error

The requested page cannot be accessed because the related configuration data for the page is invalid.

Detailed Error Information:

Module
   IIS Web Core 

Notification
   BeginRequest 

Handler
   Not yet determined 

Error Code
   0x80070005 

Config Error
   Cannot read configuration file due to insufficient permissions  

Config File
   \\?\E:\SCCMContentLib\web.config 

Requested URL
   [URL unfurl="true"]http://xxx-sccm-02-xxx.xxx.local:80/SMS_DP_SMSPKG$/xxx00002[/URL] 

Physical Path
   E:\SCCMContentLib\xxx00002 

Logon Method
   Not yet determined 

Logon User
   Not yet determined 

Config Source:
   -1: 
    0:

Can anyone please throw some ideas in my direction?

Many thanks.