PHPExcel:找不到此工作簿的默认样式

I'm trying to convert xlsx to pdf with PHPExcel+DOMPdf and get this exception: "No default style found for this workbook".

Here's some stack trace:

Warning: Invalid argument supplied for foreach() in /var/www/clients/client46/web339/web/phpexcel/Classes/PHPExcel/Reader/Excel2007.php on line 365

Warning: Invalid argument supplied for foreach() in /var/www/clients/client46/web339/web/phpexcel/Classes/PHPExcel/Reader/Excel2007.php on line 402

Warning: Invalid argument supplied for foreach() in /var/www/clients/client46/web339/web/phpexcel/Classes/PHPExcel/Reader/Excel2007.php on line 1715

Fatal error: Uncaught exception 'PHPExcel_Exception' with message 'No default style found for this workbook' in /var/www/clients/client46/web339/web/phpexcel/Classes/PHPExcel.php:930 
Stack trace: #0 /var/www/clients/client46/web339/web/phpexcel/Classes/PHPExcel/Writer/HTML.php(142): PHPExcel->getDefaultStyle() #1 

I've also tried tcpdf, but I keep getting this error as well.