That video didn't show much. Is the footswitch plugged in? I believe with the footswitch plugged you can only switch channels with that, the button on the face of the amp only works if there's no footswitch plugged in. That's how my Dsl works.
Welcome to the forum, what Scozz says is true if the footswitch is plugged in it must be switched from it, if it is not plugged in and won’t switch from the panel it’s tech time, I have seen a dsl40c with that problem in a SamAsh