Why is GPT 4 not recognizing any uploaded pdf file since 10 days?

Initially, gpt 4 was working perfectly fine. However, in the last 10-12 days gpt 4 has neither been able to recognize or read any uploaded file nor is it responding to the questions according to the file uploaded. I believed it to be a bug due to ongoing work in the backend however it’s been more than 12 days now. Can anyone help with this issue?