ChatGPT 4 forget the context

I asked ChatGPT to code a sendemail function and he wrote me a class (it is ok for me). After, few discussions later, I suggest him to add informations on the sendmail. But he wrote me a function instead of modifying the previous class he
Do you know why did he forget the context ? Are there any solutions or I have to descrived all the details again before I request him something ?
Best Regards, Sam.