Then you will need to know how you have to configure that LDAP. Engage with your IT to know which fields are relevant for the authentication of users.
With regards to the web server service, verify whether it is supposed to be using IIS or QlikView Web Server. There could be issues related to the DSC and users not getting memberships resolved and so on, but if the services don't work it's a completely different issue.
So start by checking the service account in all servers with the same username and password, that they are a domain account, that they belong to the local Administrators and QlikView Administrators group and move from there.
I could see the access point is still running and have no issues. However, it could see the error for LDAP (xyz.abc.com)stating "setting up connection failed, the server is not operational" in event log. The server is still down in QMC
How to resolve this ?
The LDAP server is not part of QlikView, the configuration of the Directory Service Connector (DSC) is. First check that the directory is the one supposed to be and then check that the configuration is what it is supposed to be.
Then, can you open all the tabs in the QMC? Of course, if QlikView Server is down, it will take longer to open the QMC part related to it but you should still be able to see something.