The way I read the original post by Usm10, the Publish Calendar option is not missing - it is there, but it is impossible to select your main calendar in the drop down list. When you do, you are returned to the same view with no calendar selected. I am able to select secondary calendars of mine, but not the main one.
I started researching this after one user submitted a ticket describing this mysterious problem. I went into my own Outlook on the web, unpublished my calendar, and was unable to select it to publish it again.
So it seems to be a problem for more than just a few...?
Hope Microsoft can acknowledge that this problem exists, and find a way to mitigate it.