Ensure that your Jamf Now account is ready for OS Updates management:
Verify that the devices in your account have iPadOS 13 or later, iOS 9 or later, macOS 10.11.5 or later, or tvOS 9 or later, and are enrolled via Automated Device Enrollment.
Ensure the devices you want to update are fully charged, or connected to a power source, and are unlocked. If a device is locked, such as via a passcode or FileVault enabled, the OS update will download but remain uninstalled. Users must unlock the device, and then manually install the OS update on their device.
Ensure devices are not in Single App Mode or they will be unable to receive OS Update commands. Deploy any OS updates before placing a device in Single App Mode. Devices already in Single App Mode will need to be taken out of this mode to receive the update.