DSXchange

Assign the roles to the Admin or Operating System credentials must match to use the datastage

When you state "Admin User" do you mean the operating system admin user (superuser) or the Information Server admin user? If it is the Information Server admin user, might that user's password have expired?
Can you get access to, say, the Reporting tab?

Just similar thing happened with me,
and I found out that it was a problem with the server system date that had been changed.
Once it was reverted to the correct date, Things worked fine.