Why is my Xbox One S stuck in Firmware update mode?

You’re welcome Al.
Keep me posted if you need to do so!

Yes, and it did not fix the problem. Plugging it in put the controller in a loop to keep needing an update.

Hello Al, this is Manuela. I'm an Independent Advisor and community user like you, ready to assist with this.
Not a Microsoft employee.

I’m sorry to hear you’re having trouble when trying to update your controllers. Let’s try to sort this out.

For this purpose, may I know if you tried:

A. Performing the update by connecting the controllers with the USB cable.

B. Using the Xbox accessories app available on a Windows PC (if you have one close to you)

Hello Al, I’m sorry to hear the inconvenience persists.

Based on all this information, it would be better to get your Xbox console inspected and repaired.
As Microsoft doesn’t offer repairs for Xbox One consoles, you may need to reach a local repair shop.

I spoke too soon. It has to be my Xbox One S causing the issue.