Proxima Not really. That looks really odd. I just installed MitID from scratch on a fresh user profile, and everything worked. I could do all activation steps.
Just double checking: Are you sure that when you installed for the first time, did you satisfy all the criteria? Locked bootloader, OEM unlocking disabled, Google Play Services, and installed from Google Play? Because if MitID "trips" due to some failing check, it will permanently taint that installation. You will need to uninstall the app and install it again.