TL;DR: In Jamf School, I am in a similar boat and have tried some things to a point where I am led to believe it may be an M1 issue, but my scope is small and have only been testing for the second day.
This is something I have started struggling with in our transition from Jamf Pro to Jamf School. I could see in the updates page that our test units were 11.4 with the update option to 11.5 or 11.5.1. Checking for the update on the device had the same result of saying 11.4 was the newest version. Devices I am testing on are M1 macbook airs and Intel macbook airs, all on 11.4.
I discovered the same payload in the macOS profile under Restrictions > Functionality > Defer for x days. By default, it was set to defer for 30 days with App updates and Software updates turned on. I changed the defer to 0 days and unticked App updates and Software updates.
Through much going back and forth of disabling and enabling the restrictions profile, the devices see the 11.5.1 update... sometimes. If the restrictions profile is turned off, it sees the update just fine. With the restrictions profile on it sees it if the updates are checked on the device, but this isn't consistent across the devices.
Pushing the updates through Jamf School on the updates pane reports a status of "Update scheduled" to "Downloading x%" up to about 10-13% then turns blank. Just managed to successfully remotely install this way on the Intel macbook, but the M1s are still failing to install remotely.
On device, I have successfully installed the 11.5.1 update manually on a device that saw the update. I also had another that saw the update and began to download about 700-800 MBs, then gave a connection error. So, 50/50. These were both on M1 macbooks.
Testing further...
Edit: spacing
