I've had one for about 2 months, and honestly the Bluetooth has been buggy since day 1, but I just had the same issue you did 2 nights ago too. In the morning it was fine, then a few hours later, there I am setting up for practice the night before a 250+ person gig and my amp is a brick. Eventually figured out it wanted an update, but for a while I was all but convinced it was fried. I couldn't do anything about it since I've never been able to update it from my android (annoying). Also, every time I've tried to update via my Windows 10 pc, I get a "file corrupt" error. So my hail Mary was to connect it to my ipad and it finally worked after like 3 tries. Long story short, I'd be surprised if your iPhone can't get the job done, but If not, iPads seem to be the only things that can reliably communicate with these amps, and if it doesn't work the first time, give it another shot.
Anyway, I've got a real bone to pick with Line6 for forcing me into a mandatory update with zero options. I was totally screwed for the entire practice. If it had been a night later I would have been standing in front of a full room like an idiot. The worst part is, my hope was that maybe this update was going to fix the annoying Bluetooth data disconnect problem it's always had, but I think it's made it worse! I had an awful time trying to connect all weekend and it still loses its data connection every time I change tones.
I really like the concept. I was very impressed with the sound I get out of a small, totally digital package. But these things have some serious bugs and Line6 needs to get on top of it quick.