I am not sure if this is a bug, but old chats I had that reached the max length are no longer able to be read at all… At first the screen will take me back to New Chat and say, "This conversation is too long; please start a new one." Then if I open the chat again, it will stay blank forever. I don’t need to be able to chat, but I like looking back at my stories in my free time, and this was one of my favorites. I have tried getting a data export, but I guess they picked and chose which chats to export, as chats that I haven’t touched in months were sent over, and only 6 conversations were sent.
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Hitting the maximum length and being unable to continue the chat is expected, but I would not expect the old conversation to become unreadable or open as a blank screen afterward.
If you haven’t already, I’d try first checking the same conversation from another browser/device and also from ChatGPT web rather than only the app. If it still opens blank everywhere, that sounds like a bug with loading archived/max-length conversations rather than just the normal “conversation too long” limit.
I also found this existing topic of similar issue and where OpenAI support recommends to open a support ticket.