Re: Upgrade IOS 9 public beta...
I was getting the same message with the same result. I got it on my iPad air 2 as well, and went to the settings and was able to upgrade from there. On my phone, in the settings, I tried going through settings and it said I was up to date. I tried restarting the phone and even plugging it physically into my computer to see if iTunes would pick up on it. No luck.
Then it hit me, go to the Apple Beta Software Program website and sign in to your program and install it from there, kind of like we did when we got the email link. Sign in, enroll your device, download the profile and then the update. Mine is downloading as I type this. I hope this helps.