[v8i] What can cause Microstation v8i to fail to upgrade v7 files to v8? MS_OPENV7 is set to 1.

One user here is having trouble with V7 .dgn files opening as V7, rather than upgrading to V8.  The documentation states that setting MS_OPENV7 to 1 will solve this, but it does not work. 

Is there something specific to the file that could prevent this from working?