Reason: The rule is not set. To set the rule, read the section Adding Places Rule in this tutorial and follow through with the steps described.
'QR-Code invalid' when making an order from the Web App link
Reason: You're trying to make an order from the content that belongs to a 'place.' You need to scan a QR Code generated for this place to proceed with the order. It is because each place has its own rule, set at the content to allow ordering with its QR Code.
For more information on generating and obtaining a place's QR Codes, read the section Managing QR Codes in this tutorial.