How to debug a file upload to S3

Hello,

I have create the following function to test out the upload form:

public function store(Request $request)
    {

        $file = $request->file('file');
        $name = MediasourceNameGenerator::generateUniqueName();
        $path = $file->storeAs('mediasources', $name, 's3');
        echo $path;

    }

the form submission works perfectly. The only issue seems to be the store into S3 bucket action.

It returns a blank page and the file isn't uploaded. Server error logs don't show anything wrong. What makes me think that's an error is the fact that the form takes several seconds to upload the very small imagine I'm trying to save.

How can I debug it?

Thanks, Simon