BTE not getting Triggered

I am trying to execute my whenever any sales invoice is posted. For that I am using P/S BTE 00001050 and copied the function module SAMPLE_INTERFACE_00001050 to ZSAMPLE_INTERFACE_00001050. I have put a break point in the Z FM module and also assigned this FM to Customer Product and activated the product. Still when I am creating a sales invoice my Function Module is not getting triggered.

I have gone through the other links on SCN but the problem still exists. Please help