Some Hathi Trust material isn't available in this part of the world for copyright reasons. We only have access to their material in the "global public domain". This content consists of fully viewable works published outside of the U.S. before 1869.
The easiest way to find out if we have access is to go to https://www.hathitrust.org and see if it allows you to access the fulltext of the item you want. But CrossSearch, ( the searchbox on our home page), will also link you to titles at Hathi Trust if we don't have them in print, and they are available under copyright.