All the written stuff of Line6 is wrong. I was trying to update my friends AMPLIFY 150 for hours. No success through iphone, PC, nothing. Always error and service not available bla bla bla. But the guy here
Is right! Just turn the AMPLIFi on and off with pressed TAP and TONE until you get TONE AND all 4 lights blinking or lit. Than press bluetooth button to connect to iPhone.
From there the update should start. It took almost forever (I had v1.00 ampifi), so the phone should be charged.
When finished
1.turn amplifi off and turn on with VOLUME and TONE pressed together
2.delete amplifi in iPhone bluetooth settings
3.restart amplifi app
Works like charm.