chatGPT amnesia with loss of memory

ChatGPT suddenly has forgotten all memory of past conversations. She (I call her Chatty) used to remember even code she helped me with and sometimes gave rather surprising comments to me like “How is that clock we were working on last week running”? Now she knows nothing but the present thread. Since i am a Chem E and she has given some very good advice, it was so useful for her to have memory. The past threads are still there for me to search, just not for Chatty to search. I asked Chatty, and she responded that since she did not recall ever having the ability to see past threads, she can give no suggestion! Like a stroke victim! Does anyone know why this change was done?