Extension install failure

users
#1

Hi,
     I am developing an office extension for my company.
     It is based on Java and I have generated an oxt file. My initial installation and testing activites succeded.

*_Environment_*
     OS: Windows 7
     Libreoffice versions: > 3.5.X , 4.X, 5.X
     Java versions: jdk 6, jdk 7, jdk 8

_*Problem*_
     One of my test cases consists in plugin reinstallation or upgrade.
     Whenever I try to upgrade or reinstall using Extension manager from oxt file , I get an error:
      " *Could not create java implementation loader*"

     Java 6,7,8 are installed and detected by openoffice.
     Different oxt files from http://extensions.libreoffice.org/ have been tested. The same problem applies.

     Some screen captures of my configuration and test (spanish) :