stake calendar has "disappeared"

As stake executive secretary, I have created a stake calendar for stake presidency meetings. This calendar is set as Private: I can edit and the president, his counselors, and the stake clerk can view. All of us are added by calling, not by name. This calendar has worked for many years with no issues. It syncs well with my Tools app, Google calendar, etc.
2 days ago on my Google calendar I noticed that there were no entries from this calendar being displayed. I opened up my Tools app and the calendar was not there. I went to the calendar and it was not showing up in the list of calendars to display. I went to Manage Calendars and it was there, as it had always been. Weird, I thought. I deleted the calendar and re-created it. Now it shows up properly on my display and all of my devices. However, now my stake president is reporting that it is gone on his Tools app and on his computer screen, just like it was for me.
Does anyone have any idea what is going on?

I'm not sure what happened in your case, but for the stake president, he probably needs to go to the website, click on "add calendars" and select it.

If it's not selected, it won't be visible on the main page.

The others may need to do the same as well.