I would like to share some experience about the OCS. The OCS service looks fine where all the services were running.
The certificates look fine and valid until middle of this next month. However, the client could not sign in.
So I took further step to investigate. I tried to log in the OCS client via internet. The OCS works fine and connect perfectly.
So, the second suspect I can think of the internal certificate, but however the certificate have not yet expired where the expiration is next year.
So, I furthered investigate the the event viewer. The event log below is related to certificate. This event ID 14398 is generated.
Also, the event ID 36883 was also generated.
The workaround that I approached is to renew the internal certificate.