I bought this amp a few weks ago and all was well with connecting to my Iphone 6s, both on the main bluetooth of the phone and the gateway app.
Then a few weeks later I tried to connect my phone and since then I only recieve the message: 'Connection Unsuccessful, make sure "CODE..." is turned on and in range'. I continue to get this message despite the amp being turned on and in range.
In addition, the amp can be connected to on other devices such as my friedns iphone and my pc.
So far I have followed the proceedures suggested of the correct sequencing, but this problem seems to be more deep rooted.
Sorry just realised I added my answer as a comment... doh! Anyway hope it helps.