NBA 2K18 servers will be shut down later this month.
If you are still playing NBA 2K18, You wo n’t be able to connect it anymore starting January 18.
According to 2K Games, any mode of earning or using VC will be affected. This includes other online features such as MyTEAM mode and online matches with other players.
You can still play offline fast games with MyGM and MyCAREER modes. Doing this will give you SP instead of VC.
If you created a MyCAREER or MyGM save file online before the server went offline, the data will no longer be available and you will have to start a new game in these modes.
As TheSixthAxis points out, considering the age of the game, shutting down the server is not surprising. NBA 2K17 has been offline in early 2019, which means that NBA 2K19 will be offline around the end of 2020.
NBA 2K20 is the latest version in the annual series.