Hello Everyone:   I have a Marshall DSL40C and it has a two button foot switch - Channel (tip) & Reverb (ring) and the plug is a TRS.  Using a TRS cable and setting the Helix to Ext Amp in global settings, I can only get the reverb to switch on/off but not the channel.  I've tried assigning the channel and reverb to foot switches and I also tried the instant command and I still cannot change the channel.  To test further I took a crappy TRS cable and swapped the tip and ring on one