Model not found error message

ChatGPT Bugs
1

I opened up a chat that I had used about a month ago to create an Excel macro. I wanted to make a couple of modifications to that macro. But after reopening that chat, everything I enter gets a “Model not found” error.

A notification with a red warning icon displays "Model not found," alongside a "Retry" button and options for copying, thumbs up, and thumbs down feedback. (Captioned by AI)
A notification with a red warning icon displays "Model not found," alongside a "Retry" button and options for copying, thumbs up, and thumbs down feedback. (Captioned by AI)438×188 6.61 KB

What is this error and what can I do about it?