Hi welcome to the forum.
Firstly does the box work with the controls revealed when you pull down the front flap ?
The humax remote controls can be set to control multiple Humax units though this is the first time I have seen one changing it’s channel from the default of 1(unless you have multiple Humax boxes in the same room).
Otherwise try switching off the box using the power switch (rear left) and powering up again say 5 minutes later). Note the box will wake up and shut down again, after this boot the box as normal.