According to a thread on Reddit and several tweets, the problem was not specific to any one device and users said that they were told their Apple IDs were locked for security reasons.
A lot of users who own an iOS device are complaining that they re getting locked out of their Apple IDs. While some took to Twitter to vent out their frustration, some have started a thread on Reddit. According to the tweets and messages on these platforms, the problem is not limited to any particular device and people who have multiple devices, claimed that they have to re log-in with all the devices. There is no word from the company on why some users were kicked out of their accounts and were told to log-in again.
According to MacRumors, users say that the process happened without warning on the iPhone, Apple TV, and other Apple devices, while they were using them. The original post on Reddit confirmed that he/she has two factor authentication enabled and a unique iCloud password for their Apple ID not used anywhere else, and many users report similar settings. Users says that they are being told that their Apple IDs were locked out due to security reasons.
When people started tagging @AppleSupport on Twitter, the handle directed all the users to Apple’s Support Communities web page which details what users should do in case they are locked out of their Apple IDs. Generally this happens if a user or someone else has entered the password, security questions, or other account information incorrectly too many times. Apple says that this behaviour of Apple ID automatically locking, is shown to protect users’ security and they can unlock the Apple ID after verifying the identity. There is no official statement from Apple on the issue.