please check all the poi api jar files.
xlsx files get corrupted mostly because of a missing jar file.
http://www.apache.org/dyn/closer.lua/poi/release/bin/poi-bin-3.13-20150929.tar.gz
i tried your project it ran without any problem and then i opened your xlsx file they all opened.
problem seem to be in jar files please delete all the jar files and download them again. selenium/poi api/testng/junit/log4j etc
Thanks Ashish , Issue got resolve now.
saxon-dom-8.7 was missing.
Appreciate you help.