2 things to try for this that may help.
1) Try going under all movies and then scroll to right, there is a group IMAX enhanced that has them all there.
2) Close out of StreamFab and go directly to D+. Go to the movie and then select to watch the IMAX version and start the movie. Then close out of D+ and go back through StreamFab.
A while ago, I had the issue and item 2 fixed it. Haven’t had it in a while so not sure if it’s still valid.