New iOS App can’t add plug

I have a Sonoff Plug (S31 from memory). Wanted to move it’s wifi network, so tried to add it new to todays updated App. Didn’t work.
It was doing the three flash thing fine.
Do I need to delete the device and lose the scenes it is in?

S26R2 Running latest firmware. I think it is 3.7.6

I’d recommend if it does not work with regular connection/join, you just use “Compatibility Mode” at the bottom of that page. It semi manual method vice automatic method.

After you get the three flashes, you must press again and hold for the red light, so it goes into "steady/repeatedly flashes, not 3 flashes.

Compatibility mode method must match Fast Flash/compatibility mode on the device too/both