IIS not able to retain the session variable

As per our application flow for authenticated user we are using Session to store different parameters & under filter config we have written custom filter on action executing to validate by checking Session variable using context.session[key] and session variable, with the flow of application its creating session variable but when we try to access it always return null. We debugged the code and its working fine in our local visual studio-2019. Only after deploying in IIS on server this issue occurs