The issue:
I have been using four boards successfully with the Calendar Power-Up for years.
A week ago one of the boards stopped syncing with Google Calendar.
The image below is of the menu from my Google Calendar. Here I can toggle on/off the display of imported calendars such as my Chores Trello board. You'll notice the second imported calendar doesn't display the name of that Trello board. That's the problematic one.

Steps I've taken to troubleshoot:
In Google Calendar I have unsubscribed from each of the Trello boards and re-added their .ics URL.
In Trello I have disabled and re-enabled the Calendar Power-Up for the problematic Trello board. As well as re-generated the .ics URL.
I have cleared my cache in Google Chrome.
I have the most up-to-date version of Google Chrome.
The problem persists with only that one board. The three others are syncing just fine.
The question:
Any idea why this is happening to only one of my boards? Or how to address it?
Any and all advice welcome. Thank you very much in advance.