Libreoffice 4.2 not responding on centos 7 with --headless

CentOS Linux release 7.1.1503 (Core)
LibreOffice 420(Build:3)

Sorry for my poor english, I have installed LibreOffice with : yum install libreoffice-headless

The Linux system has no serverX installed. I tried to make pdf conversion using command line :

cd /home/test-conv-to-pdf/;

soffice --headless --convert-to pdf Simple_Resume_Vol1.docx

even with

soffice --invisible --nologo --headless --convert-to pdf Simple_Resume_Vol1.docx

And the command does not respond …

The same on Windows 7 and libreoffice 5 is Ok.

Any hints ? Thanks by advance !