If you are not familiar with the oc command, refer to OpenShift - Getting Started with the oc command.

Let's say you are attemp to login to OpenShift using the oc login command and Error from server (InternalError): Internal error occurred: unexpected response: 500 is returned.

~]$ oc login -u john.doe
Authentication required for https://api.openshift.example.com:6443 (openshift)
Username: john.doe
Password: 
Error from server (InternalError): Internal error occurred: unexpected response: 500

I once had this issue when I updated the htpasswd identity provider to use a different htpasswd file. I used the oc get users command and noticed that new users jack.doe and josh.doe had a different identity than prior users jane.doe and john.doe.

~]$ oc get users
NAME            UID                                    FULL NAME       IDENTITIES
jack.doe        2d5443d8-bc39-4389-91b3-b6a1e53c26f4                   htpaswd:jack.doe
jane.doe        ad0d5d38-ad19-4e62-868f-f03e85897f1d                   htpasswd_provider:jane.doe
john.doe        127a869c-342a-4ea4-9f8e-9945276dc842                   htpasswd_provider:john.doe
josh.doe        8eaf0f35-ddc7-4410-a477-36fc1430b2bc                   htpaswd:josh.doe

I saw similar output with the oc get identities command.

~]$ oc get identities
NAME                           IDP NAME             IDP USER NAME    USER NAME       USER UID
htpasswd_provider:jane.doe     htpasswd_provider    jane.doe         jane.doe        ad0d5d38-ad19-4e62-868f-f03e85897f1d
htpasswd_provider:john.doe     htpasswd_provider    john.doe         john.doe        127a869c-342a-4ea4-9f8e-9945276dc842
htpasswd:jack.doe              htpasswd             jack.doe         jack.doe        2d5443d8-bc39-4389-91b3-b6a1e53c26f4
htpasswd:josh.doe              htpasswd             josh.doe         josh.doe        8eaf0f35-ddc7-4410-a477-36fc1430b2bc

To resolve this, I deleted the prior users jane.doe and john.doe.

~]$ oc delete user jane.doe
user.user.openshift.io "jane.doe" deleted

~]$ oc delete user john.doe
user.user.openshift.io "john.doe" deleted

And also deleted the prior identities jane.doe and john.doe.

~]$ oc delete identity htpasswd_provider:jane.doe
identity.user.openshift.io "htpasswd_provider:jane.doe" deleted

~]$ oc delete identity htpasswd_provider:john.doe
identity.user.openshift.io "htpasswd_provider:john.doe" deleted

And then john.doe and jane.doe were able to sign in.

~]$ oc login -u jane.doe
Authentication required for https://api.openshift.example.com:6443 (openshift)
Username: jane.doe
Password: 
Login successful.


~]$ oc login -u john.doe
Authentication required for https://api.openshift.example.com:6443 (openshift)
Username: john.doe
Password: 
Login successful.

And then the oc get users command showed the users all had the same identities.

~]$ oc get users
NAME            UID                                    FULL NAME       IDENTITIES
jack.doe        2d5443d8-bc39-4389-91b3-b6a1e53c26f4                   htpasswd:jack.doe
jane.doe        00e05945-f219-4a43-a3e0-3946a749510f                   htpasswd:jane.doe
john.doe        0e72aa79-0014-4c55-9484-2ca6fcf1211a                   htpasswd:john.doe
josh.doe        8eaf0f35-ddc7-4410-a477-36fc1430b2bc                   htpasswd:josh.doe

And the oc get identities command show the users had the same identity provider.

~]$ oc get identities
NAME                 IDP NAME    IDP USER NAME    USER NAME       USER UID
htpasswd:jane.doe    htpasswd    jane.doe         jane.doe        ad0d5d38-ad19-4e62-868f-f03e85897f1d
htpasswd:john.doe    htpasswd    john.doe         john.doe        127a869c-342a-4ea4-9f8e-9945276dc842
htpasswd:jack.doe    htpasswd    jack.doe         jack.doe        2d5443d8-bc39-4389-91b3-b6a1e53c26f4
htpasswd:josh.doe    htpasswd    josh.doe         josh.doe        8eaf0f35-ddc7-4410-a477-36fc1430b2bc