Selector not working for sliverlight application in production

Hi ,
I just worked on the process of sliverlight application where it is working fine in dev and QA fine (unattended mode )… but when it comes to production it is unable stopping at particular activity .Unable to find the selector .When I just want locate the selector in production also But its not identifying .(Thing is previous selectors , activities worked).
any help on this ?
(checked version Silverlight .it is same in three environments)

@loginerror @Palaniyappan Can you please help on this …

If it is working on 2 environments and not in a 3rd, then you should seek for what may be different there… If you are 100% sure the application is the same, maybe something in the robot production pc is not the same, maybe the extension?

It is the same one … have to check extension may be