If your phone is still stuck on a “classic” system such as iOS 11 or macOS 10.13 (High Sierra), then pay attention.
An exposed Apple internal document shows that the company plans to close Apple support services for these legacy systems in May, including Apple Music, Apple Arcade, Apple TV+, Apple Fitness+, Apple News+, etc.
In other words, the only Apple core service available is iCloud.
It is reported that Apple released iOS 11, macOS High Sierra, watchOS 4, tvOS 11 and other operating systems in 2017, and it has been almost 6 years so far.
Fortunately, if you want to continue to use it, you can just update the system. After all, iOS 11 devices can be upgraded to iOS 12.
Finally, sort out the affected operating systems this time:
From iOS 11 to iOS 11.2.6
From macOS 10.13 to macOS 10.13.3
From watchOS 4 to watchOS 4.2.3
From tvOS 11 to tvOS 11.2.6