When I slide the crossfader, the sound doesn’t change.

Crossfader assign may not be set the way you want the crossfader to work.

In the general setting, channels [1] and [3] should be set to [A] and channels [2] and [4] should be set to [B] .

*Crossfader assign sets the channel output to either the left or right side of the crossfader. If you don't want to use the crossfader, you can change the setting to [THRU] to disable it.

For details, refer to the Operating Instructions > "Part names and functions" > "CROSSFADER ASSIGN switches".

You can read the Operating Instructions [here].