If you notice that you cannot check the infinite qty option, make sure your product and it's condition variant:
Has a price
Has at least 1 quantity
These two are required to check / toggle the infinite qty option.
If you are unable to check toggle the infinite qty check box option
If you notice that you cannot check the infinite qty option, make sure your product and it's condition variant:
Has a price
Has at least 1 quantity
These two are required to check / toggle the infinite qty option.