Earlier today, many users have reported being kicked out of online matches, while others are not able to connect to online games on PS4. Sony has caught wind of the reports and is working on a solution.
Users affected by the issue get kicked out of online sessions for games such as Killzone: Shadowfall, Call of Duty: Ghosts and Battlefield 4. They also get a message asking them to get a PlayStation Plus subscription to play online, and as you may have guessed, they already have one.
A Sony employee has responded to the matter on Twitter confirming to users that their PS Plus subscription is fine, and adding that they are investigating the issue.