Just this morning I had to do the identical wifi network config 3 times to get iOS app to work. On 3rd attempt it worked and I'm now up & running. Problem 'may' have been powering down (as you described in step 2) the 3rd time I did it I just inserted the SD card while Devialet was on and streaming. iOS came online immediately and worked like a charm!
Statements in my posts are opinion only, not to be construed as fact. Any projects I engage in are at my own risk! Their outcome cannot be assured and may result in success, small/no change or catastrophic failure. I encourage no one rely on anything I say or do as gospel and to realize your mileage may vary!