I tried that already and it doesn't work. I press and hold the button and it starts flashing slowly, then flashes quickly, but it never shuts off. The next time I start the printer the wifi is back on and it appears on the network.
That worked! Thank you so much. Your image also helped me find the Pro-10 online manual which I hadn't seen before (not sure why). It says it's supposed to blink 12 times to shut off the wireless, but 11 worked as well!