A bug in Apple’s macOS software update process is causing issues for Mac system administrators and mobile device management deployments.
As noted by microMDM, the issue surfaced after the release of macOS Big Sur version 11.1. There were widespread reports of system administrators not being able to see the software update, or not being able to download and install it.
Apparently, the cause of the issue is the fact that macOS 11.0.1 and macOS 11.1 hosts are requesting that update servers send over macOS 11.0.1 instead of the next available software update. Because of that, the server rejects the request because a machine already has 11.0.1 installed.