Aha, finally figured it out. The instructions on the cheat-sheet say:
'...press and hold the LED pushbutton for about 3 seconds until the LED flashes...'
So that's exactly what I was doing: holding the LED pushbutton until the LED flashes, and then if I interpret the brief 'off' of the LED as a flash', then I released the button because the instructions say: 'hold UNTIL the LED flashes.'. If I ignore the instructions and continue to hold the pushbutton, then I can change patch.
My suggestion is that the instructions are misleading. You do not hold the pushbutton until the LED flashes! You keep holding it down long after it flashes!
The instructions should say something like:
To change patch, press and hold down the LED pushbutton. After about 3 seconds, the LED should briefly flash - you are now in 'patch select' mode. Continue holding the pushbutton down and select the patch using the A and B knobs. The A knob selects between 5 banks, and the LED will change colour between red and green as you move the knob so that it is selecting another bank. The B knob selects between 8 patches in a bank, and again the LED will change between red and green as the knob is rotated. When you have set the A and B knobs to the desired patch, then release the pushbutton. The patch should now be active.
Here's a nested activity graph:
Hold the button down
----Select patch bank using A knob
------LED will go red/green for each bank
----Select patch number using B knob
------LED will go red/green for each patch
Release the button