Configuring a Randall RF4 footswtich to work with a Mod 50

[mfred]

I recently picked up a Randall RF4 footswitch believing that it would work with my Egnater Mod 50 for channel switching. I plugged the footswitch into the "Midi In" on the back of the amp. The footswitch lights up but doesn't change the channels. Can anybody help me on how to configure it to work with the Mod 50. I tried holding the Mod 50 channel switching switch in for three seconds like the owners manual states but nothing happened. Thanks