All the 25 amp presets on BIAS Head/Rack are assigned to MIDI Program Change #0 to#24 as their factory defaults, which means you will need to keep the MIDI# slots empty first, then assign different MIDI PC number to each one:  

1: Connect BIAS Head/Rack to computer/iPAD via USB/Bluetooth.
2: Select MIDI Settings in Settings Menu.

 

3:Click on Program Change Tab.



4:Select an amp preset and assign it to a different MIDI PC# on the dropdown list.