codeigniter 3.1.9 session failure

am building a project and apparently my session works and sometimes stops working.when i post that data to the first controller and access it using a session it works but when i want to access it in other controllers and views it does not.

Since you have not provided additional information in the form of a piece of code where you work with sessions or logs from writable/logs/.
I can assume that you initialized the session class in only one method in which it works for you, and in the one to which you refer to this initialization is not...
You must initialize the library in each controller method for it to work.
If you do not want to do this in each method then it is highly recommended to use models.

I would change this world, but God doesn't give me the source.