Issue resolved now.
the service account running SQL Server didn't have permissions on the clustered Disk "S"(in our case) to create temp mdf and ldf files.
After we have full permission to the service accounts, tempdb got created and we were able to start sql server.
Another issue that I sense here is that the customer wanted to create Tempdb mdf and ldf files in the root directory(S
I guess, had he created the tempdb in a folder within S Drive like S:\Tempdb, the permission issue wouldn't have happened.
Can someone pls confirm if the root directory of any drive needs special permissions?