Cannot enter Product ID in Loyalty benefit

Hi experts,

I am try to implement the benefit function in CRM Loyalty Benefit. I have add "LOY_BENEFIT" set type to a hierarchy and then assign a product to this hierarchy. In the "LOY_PRO" role, I can see the product as the below picture.

However, when I try to create a benefit, I find the "Product id" is disabled. Is anyone can give me some advice?

Thanks a lot,

Best Regards,

Molly Xin