Invalid status on head request

Dear Grzesiek,
You helped me previously, so I was wondering if you could be able to help me on that. We got this error message when a friend tried to send me filled forms. I'm scared that everything will be deleted or lost.
Thank you a lot.

Médiha (Tunisia)

It's a form he tries to send to Google Sheets right?
If so please make sure a Google account is selected in General Settings->Server before trying to upload your data.