[Flow] Using PHPExcel with Flow after update

[Daniel Völkel]

Hi guys,

I have built an application that uses phpexcel in some actions and worked fine. Now, after updating Flow to the latest version, I always get the following error message:
Fatal error: Class 'PHPExcel' not found in ...

I'm calling the class like this:
$objPHPExcel = new \PHPExcel();

Of course, phpexcel is listed in the active package list.

Do you have any idea what could cause the problem? 

Best regards,
Dan