Downgrading to iOS 17.3.1 no longer possible
Apple has made it so that iPhone users can no longer downgrade to a previous version of iOS 17.3.
The signing of iOS 17.3 has stopped to prevent iPhone users from going down to the said version. On March 5, Apple released iOS 17.4 which introduced a new emoji, app system changes in the EU, and others. Apple routinely stops the signing of old operating systems to encourage users to upgrade to safer and improved versions on their Apple devices.
Users who update to newly-released versions can keep their devices up to date and prevent data theft and attacks. Currently, iOS 17.4 is the only one that can be downloaded by the public. Those who are still on iOS 17.3 can update to the newest version by going to their device’s Settings and System, then download it and wait for the reboot.