You keep getting the message said "Sorry! Could not find SKU."
It means your product on Ali Express which their suppliers didn't have any SKU on that product so you can't order the product.
You need to find another similar product of another supplier > Override that product > and please help us to check the SKU in Variants section in our app Product list > Edit product section
If the SKU is available, then you can simply use it to fulfill your current order
Please let me know if you need some more help.