Upload pdf file fails

I try upload file image and working fine, but why not work with pdf file?
i got error "The file requirement is not a valid uploaded file". whats wrong?

PHP Code:

$validationRule = [
            'file' => [
                'label' => 'File Upload',
                'rules' => [
                    'uploaded[file]',
                    'mime_in[file,application/pdf,application/force-download,application/x-download]',
                    'max_size[file,5120]',
                ],
            ],
        ];
        if (! $this->validate($validationRule)) {
            $errors = $this->validator->getErrors();
            $error = array_shift($errors);

            dd($error);
        } 


---

after dd($file = $this->request->getFile('file')); originalMimeType is empty string.

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This issue has been resolved. It seems the file I tried to upload was broken, but I don’t know why that file can still be opened and read normally with a PDF reader like Preview in Mac.

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