Recurring issue with uploading and reading PDF files in ChatGPT

Hello,

For several days, I have been experiencing an issue with uploading PDF files in ChatGPT.
	•	I can upload a file successfully.
•	A few minutes later, the file becomes inaccessible, and ChatGPT can no longer open it.
•	I have tried with several PDFs (around 4 MB), but the issue persists.
•	No specific error appears at the time of upload, but ChatGPT fails to read the files after they are sent.

Could you help me resolve this issue? Is there a hidden limit on how long uploaded files remain accessible?

Thank you in advance for your assistance.

Best regards,

Sergio