I’m experiencing the same issue. The only change on my end was switching from ChatGPT Plus to the Free version. My conversations still appear in the list, but I get a 404 error when trying to open them on the iOS app. I also see this message on desktop version:
“Project not found or insufficient permissions. Please verify the project exists, and ensure that your account has the necessary permissions and that there are no workplace restrictions preventing access.”
My project folders have also disappeared. I don’t understand what’s happening.