I have already installad iOS11 Beta 1 with Apple Beta Software Program.
But there are new beta releases (Beta 2 and Beta 3), when I navigate to settings-general-software update, it says,
iOS 11.0 Your software is up to date
I have also checked version, it's 11.0 (15A5278f) which is actually Beta 1.
Why don't new updates appear in software update section? How can I install new beta versions?