In order to get the SEPA QR Code visible at the checkout/payment in your website and to it working well in, you have to do 3 things:

1 - Go to Accounting/Invoicing and activate in the settings the option "SEPA QR Code"

2 - Go to the payment acquirers page and in the Wire transfer option be sure that in the tab configuration the option "Use SAPE QR Code" is checked.

3 - Last but not least, be sure that your bank account is fully set up, with all the information about your bank (see pictures below).