In the patch notes for a new Xbox Series X firmware update, Microsoft acknowledges an issue where controllers disconnect from the console.
“We’re aware of an issue in which some Xbox Series X|S controllers are losing connection with the console,” Microsoft says via a post on the Xbox support website.
While unfortunately the latest firmware update does not correct this issue automatically, they suggest a workaround:
If you see this behavior, try reconnecting the controller to the console wirelessly or with a USB cable, or if possible, connecting another controller and then submitting feedback. Then reboot the console and try reconnecting the controller.
By the way, the Xbox wireless controller has a console sync button next to the USB-C port. There’s also a sync button on the front of the console.
I had this happen to me earlier in the week. Hopefully they come up with a permanent solution soon so that people won’t lose connection to their shiny new Xbox Series X consoles.