Alternative BOM

Hi experts,

I am producing same HALB from 2 different raw materials, when a process order is created for that HALB system should ask the production version to select but its not asking, I have maintained the production version with same valid from date and with same master recipe and given 2 as alternative BOM for that HALB, but still when I am creating process order system is picking the first BOM and not asking anything, where I am missing in this, please help me.

Thanks & Regards,

Karad D D