EP1-KP
Momentary toe switch connected to a second output, works with some devices, but not the AX8.
10 inches long.
SP1
Latching toe switch connected to a second output, works with AX8
9 inches long.
The AX8 is expecting a latching switch. The switch contact must MAKE and hold, for the AX8 function to work.
So, yes, you are missing something. The AX8 wont work properly with the momentary switch in the EP1-KP. It would only work if you held the switch down permanently with your foot, and then obviously the pedal could not be rocked to modulate the chosen effect like Wah or volume. The switch could be stuck down with adhesive tape though. Or, maybe its a standard size switch, so you could swap it.