Our AI provider released a new capacity (creating multiple chats) but this removed from your visibility previous chats. We immediately told them doing this without warning us was a bad move, so we're working on a way to prevent this from happening in the future.
In the meantime, know that your conversations are not lost, they're just not appearing to you anymore. Reach out to support, let us know what exactly your conversation was about and when it occurred, and we'll retrieve it for you.