First make sure that you are sending the appropriate LDAP attributes from CAS. It might be that what the code is expecting is not being release from your CAS instance. We had the issue with lastname not being available.
Next, make sure that your username either matches what is in the code or modify it to what your institution uses. In uthsc-wpcas.php change:
return get_user_by( 'login', $cas_attributes['uid'] ); to return get_user_by( 'login', $cas_user );
