Possible causes are:
- Not all smartphones, tablets and operating systems are supported.
- If your smartphone or tablet is set to 'developer mode' or 'USB Debugging', the app cannot be installed. Switch off 'developer mode' and 'USB Debugging' and try again.
- If your smartphone is 'jailbroken' (Apple) or has been in the past, the app cannot be installed.
- If the operating system is an Android variant (also called a 'custom ROM'), such as LineageOS or Pixel Experience, then the Payconiq by Bancontact app cannot be installed for security reasons.