Devices enter the quarantine group when they break one or more of the rules defined in their normal device group. Each time SimpleMDM communicates with a device, it checks to see if the device is compliant. If it isn't, SimpleMDM moves the device to the quarantine group and updates the configuration on the device to match the configuration of the quarantine group.
Sometimes a device may appear in the quarantine group showing no violations. This often occurs because the rules of the device's normal group have changed. When these changes are detected, SimpleMDM attempts to move the device back to its normal group and restore its configuration.
If a device does not respond to SimpleMDM for this change, the configuration changes are queued and delivered to the device once it does finally respond. In the meantime, the device remains in the quarantine group.