SKU scanning by USB scanner

Dear team,

I installed Commerce POS as below demo link:
http://marupos.com/commerce_pos/login
user: Cashier01
pass: 123456

Item list:
SKU 9999990010001
SKU 9999990010002

Can you help to check the issue as below:
1. When I use SKU input by scanner (SKU COde + ENTER) --> no feedback
2. When I input manually the Product Variation ID + ENTER --> Work well
--- The example Product Variation ID is: 1 or 2

Can you tell me what step that I am missing?

Thanks,