You do not state which Humax model of recorder you have.
From what you say you appear to have one of 9200t, 9150t or 9300t. With all these models it is not possible to have both padding and series recording at the same time.
To quote from the manual:
“Auto tracking, split and series reservation are enabled only when Recording’s Start/End Time in the menu is set to On Time.”
To return to being able to use series link you need to go to the recording options and select 'on time' for both the start and end time options.
To navigate to the start and end time options press the MENU button and then press ‘1’.
NS, October 2011