Outlook keeps asking password for authentication after a second exchange server added and DAG created

I had installed a second exchange server in domain. Then some of users reported their Outlook is keep asking password, the correct password cannot be authenticated. OWA and ActiveSync on mobile are fine. Other users do not have any issues, so far around 5 of users reported the same issue on their Outlook.

• Exchange Server Standard 2016

After the second exchange server installed, Autodiscover error event id 1 appears in event log.

Unhandled Exception "Object reference not set to an instance of an object." Stack trace:    at Microsoft.Exchange.AutoDiscoverV2.FlightSettingRepository.GetHostNameFromVdir(ADObjectId serverSiteId, String protocol)    at Microsoft.Exchange.AutoDiscoverV2.AutoDiscoverV2.ExecuteOnPremEndFlow(AutoDiscoverV2Request request)    at Microsoft.Exchange.AutoDiscoverV2.AutoDiscoverV2.Execute(AutoDiscoverV2Request request, ITenantRepository tenantRepository)    at Microsoft.Exchange.AutoDiscoverV2.AutoDiscoverV2HandlerBase.<>c__DisplayClass11_0.<ProcessRequest>b__0()    at Microsoft.Exchange.Common.IL.ILUtil.DoTryFilterCatch(Action tryDelegate, Func`2 

Used below PS to update second server CAS Uri

Set-ClientAccessService -Identity "EX-Server" -AutoDiscoverServiceInternalUri https://autodiscover.domain.com/Autodiscover/Autodiscover.xml

Confirmed the CAS Uri is correct on both exchange servers.

Checked https://support.microsoft.com/en-au/topic/autodiscover-event-id-1-after-installing-exchange-server-2019-cu3-or-exchange-server-2016-cu14-93850e62-4cf4-8a76-5fd4-c8ce6f032015

PS applied>

Add-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010

Still got "A parameter cannot be found that matches parameter name 'ExternalUrl'" with below command in Exchange Shell

Get-AutodiscoverVirtualDirectory -Server $env:COMPUTERNAME | Set-AutodiscoverVirtualDirectory -ExternalUrl "https://autodiscover.365labs.net/Autodiscover/Autodiscover.xml"

Microsoft Remote Connectivity Analyzer on Exchange server with failed accounts

The Microsoft Connectivity Analyzer failed to obtain an Autodiscover XML response.

Additional Details

An HTTP 401 Unauthorized response was received from the remote Unknown server. This is usually the result of an incorrect username or password. If you are attempting to log onto an Office 365 service, ensure you are using your full User Principal Name (UPN).

Microsoft Remote Connectivity Analyzer on Exchange server with success accounts

Now the users cannot use Outlook app on desktop.

Checked forums found similar and exactly same issue but no fix provided.

It is appreciated anyone can point out which part is the root cause.