Silk Test 16.0 on Firefox 35

After installing SilkTest 16.0 was not installed xpi for Firefox .
We try to install .xpi of silk 16.5 , but still the Silk Test Workbench Script does not work. Open Firefox, but other actions are not performed . This behavior only open the browser also occurred without having installed the XPI .
The version of Firefox that we are using for testing is 35 .

Note : IE and Chrome runs correctly.