If at all possible, wear of the appliance should not be interrupted during an illness. If the illness really is incompatible with wearing the appliance, we recommend finding a short time to wear it during the day and, if possible, sleeping with it during that period, without activating it. Once your child has recovered, you should book an extra appointment with the orthodontist to have the appliance adjusted to the mouth and possibly to change the activation schedule. Don't keep turning the screw on the appliance as usual if it isn't being worn for the recommended time.
This answer is for general information. Your own case needs an examination by an orthodontist.