This can happen if you do not have a Sodexo4you account. To resolve the problem:
remove your Sodexo card from the Payconiq by Bancontact app via the menu on the left side of your screen by selecting the Payment methods and your Sodexo Card. Then choose "Remove the card".
Create then a Sodexo4you account via the following link.
Go back to your Payconiq by Bancontact app and add your Sodexo Card again via the menu at the top left of your screen. Select Payment methods and "Add a card" under the heading ‘Your meal vouchers’.