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Hi <br />
<br />
Did you try to login with &nbsp;Active Directory authentication..? Or try with Administrator@vsphere.loca<wbr />l
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it doesn't matter if I try AD account or administrator@vsphere.loca<wbr />l. &nbsp;Right now the only thing that I can log into is ESXi host.<br />
<br />
Also the VCSA Application Management - Services shows:<br />
Licensing Service - &nbsp;Healthy with errors - The lookup service is not reachable.
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After running vCenter Server 6.7u3 I added the Active Directory module. It wanted me to restart VCSA and when I did that I can no longer open or log in to vCenter<br />
&quot;An error occurred while sending an authentication request to the vCenter Single Sign-On server&quot;<br />
<br />
vSphere-Client<br />
&quot;A server error occurred.<br />
[400] An error occurred while sending an authentication request to the vCenter Single Sign-On server - An error occurred when processing the metadata during vCenter Single Sign-On setup - Failed to connect to VMware Lookup Service - <a href="https://VCSA67.corp.rsidpm.local:443/lookupservice/sdk" rel="ugc">https://VCSA67.corp.rsidpm.local:443/lookupservice/sdk</a>.<br />
Check the vSphere Web Client server logs for details.&quot;<br />
<br />
vSphere web UI<br />
&quot;[400] An error occurred while sending an authentication request to the vCenter Single Sign-On server - An error occurred when processing the metadata during vCenter Single Sign-On setup - Failed to connect to VMware Lookup Service - <a href="https://VCSA67.corp.rsidpm.local:443/lookupservice/sdk" rel="ugc">https://VCSA67.corp.rsidpm.local:443/lookupservice/sdk</a>.<br />
Back to login screen&quot;
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After running vCenter Server 6.7u3 I added the Active Directory module. It wanted me to restart VCSA and when I did that I can no longer open or log in to vCenter
"An error occurred while sending an authentication request to the vCenter Single Sign-On server"

vSphere-Client
"A server error occurred.
[400] An error occurred while sending an authentication request to the vCenter Single Sign-On server - An error occurred when processing the metadata during vCenter Single Sign-On setup - Failed to connect to VMware Lookup Service - https://VCSA67.corp.rsidpm.local:443/lookupservice/sdk.
Check the vSphere Web Client server logs for details."

vSphere web UI
"[400] An error occurred while sending an authentication request to the vCenter Single Sign-On server - An error occurred when processing the metadata during vCenter Single Sign-On setup - Failed to connect to VMware Lookup Service - https://VCSA67.corp.rsidpm.local:443/lookupservice/sdk.
Back to login screen"

Errors after enabling SSO with AD - Cannot get into vCenter

Active Directory (AD) is a Microsoft brand for identity-related capabilities. In the on-premises world, Windows Server AD provides a set of identity capabilities and services, and is hugely popular (88% of Fortune 1000 and 95% of enterprises use AD). This topic includes all things Active Directory including DNS, Group Policy, DFS, troubleshooting, ADFS, and all other topics under the Microsoft AD and identity umbrella.

Active Directory

VMware, a software company founded in 1998,  was one of the first commercially successful companies to offer x86 virtualization. The storage company EMC purchased VMware in 1994. Dell Technologies acquired EMC in 2016. VMware’s parent company is now Dell Technologies.

VMware has many software products that run on desktops, Microsoft Windows, Linux, and macOS, which allows the virtualizing of the x86 architecture.  Its enterprise software hypervisor for servers, VMware vSphere Hypervisor (ESXi), is a bare-metal hypervisor that runs directly on the server hardware and does not require an additional underlying operating system.