Cannot setup new Photon P0 unit from 2015

Hello, I just dug out an old Photon that’s brand new from 2015. I’m trying to use the Particle App on iOS and I also tried the website to set it up. I’m pressing the SETUP button for 3 seconds and the Photon does not start to blink. Any ideas? Back in 2015 was there a different way to put it in Wifi setup mode?

Thanks.