A few days afer the release of iOS 10.3.1 on the market, Apple took the step of blocking the downgrade to iOS 10.3 and iOS 10.2.1 versions that were previously available and one look at which is still more up-to-date, and they have lost support for signatures. Unfortunately, it’s no longer possible to go back to iOS 10.3 or iOS 10.2.1.
At this time, users who have transitioned to iOS 10.3.1 will no longer be able to download their device to iOS 10.2.1 or iOS 10.3. To encourage users to stay up-to-date, Apple discontinues support for signatures that regularly update older software updates after they release new versions. I mean, this step is a usual situation for the company.
iOS 10.3.1 is now the only version of iOS 10 that can be installed on iOS devices. Other than this, developers and public beta users (public beta software program) can download the beta version of iOS 10.3.2 to their device, and they can go back to iOS 10.3.1.