Yes, it IS strange. It still appears (and works) on my ROKU 4, and my ROKU TV, but not on my 4661 Ultra.
Also, as I mentioned in my previous post, when I log into my ROKU account, it appears using the search function, and it also indicates that it is installed.
I did the usual restarting, updating, etc., etc., on the 4661, but no joy. It doesn't appear on my home screen.