Make sure to accept all app permissions during the enrolment process. To function correctly, the app needs you to allow notifications and access the camera for scanning the QR code. If you refuse those permissions, the app will not work and the enrolment process will be blocked, even though it appears to be loading.
To solve this, either go to your application list and give the EU Login Mobile app the needed permissions (authorise notifications and camera access), or uninstall and re-install the app. Once done, restart the enrollment process and please make sure you grant the required permissions.