Virtual Characteristics NOT working, BADI is not call

Hello Experts,

I have a query built on Multiprovider, I had a requirement where I had to make use of virtual char though I haven't used it before.

I followed steps given in White paper available in SCN on virtual char but seems like BADI I written for Virtual Char is not being called.

May I have necessary checks that I need to make sure that can cause BADI not being called.