Try to Converge your external PSC to Embedded as mentioned in below steps.
1. Please mount vCenter ISO with same version as you have on vCenter/PSC.
2. Click on "Home" >>> Menu >>>Click on "Administration"
3. Click on "System Configuration"
4. Select vCenter "vCenter Server with external Platform Services Controller"
5.Click on "CONVERGE TO EMBEDDED"
6. It will give below warning:-
"vCenter Server downtime
Converging this node will restart all the vCenter Server services on it making it inaccessible until the operation is complete"
7. Click on proceed
8. Enter SSO (Single Sign-On) User Name & Pwd
9. Don't change "Skip AD Join"
10. Acknowledge it .
11. Click on "CONVERGE"
12. Monitor it for few min.
13. It will give vCenter Server downtime alert (The vCenter Server services will be restarted and might take a few minutes to complete. You will be logged out during this operation. Monitor the progress of the convergence from the CLI or any linked vCenter Server)
Be Patience!!!
14. Wait for sometime to come your vCenter back check via ssh with below cmd (it shouldn't show services in "StartPending")
service-control --status --all
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Stopped:
vmcam vmware-imagebuilder vmware-mbcs vmware-netdumper vmware-rbd-watchdog vmware-vcha vsan-dps
Running:
applmgmt lwsmd pschealth vmafdd vmcad vmdird vmdnsd vmonapi vmware-analytics vmware-certificatemanagement vmware-cis-license vmware-cm vmware-content-library vmware-eam vmware-perfcharts vmware-pod vmware-postgres-archiver vmware-rhttpproxy vmware-sca vmware-sps vmware-statsmonitor vmware-sts-idmd vmware-stsd vmware-topologysvc vmware-updatemgr vmware-vapi-endpoint vmware-vmon vmware-vpostgres vmware-vpxd vmware-vpxd-svcs vmware-vsan-health vmware-vsm vsphere-client vsphere-ui
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15. When all services are come up then login back in your vCenter via https://vCenterIP or FQDN/
16. Go back to below options:-
Administration >>> System Configuration >> and you will see that conversion has been completed.
"vCenter Server with embedded Platform Services Controller"
17. Now Select PSC Controller >> DECOMMISSION PSC.
Alert ##### vCenter Server downtime (Decommissioning this node will restart all the vCenter Server services. The vCenter Server will be inaccessible until the operation is complete)
18. Click on Proceed.
19. Click on "View Thumbprint" >> Enter "SSO Credentials" >> Acknowledge it>> Click on "DECOMMISSION"
20. Monitor it for few min.
21. On 50% it will give message like this.
"External Platform Services Controller node shutdown successful"
Be Patience!!!
22. vCenter Services will go down now and you need to wait to come services up
via ssh >>> service-control --status --all
23. When all services come up, login in vCenter again via https://vCenterIP or FQDN/
24. Validate only vCenter Component will show under.
Administration >>> System Configuration >> and you will see vCenter with Embedded only .
"vCenter Server with embedded Platform Services Controller"
That's it