Lost Authenticator App (registration)

I have setup my account to use 2 way authentication and I know I have used that succesfully in the past. Somehow I lost the Nuki registration in my authenticator app. I can no longer logon to Nuki web. What is the procedure in this case? How can I add Nuki to my authenticator app if I cannot get a qr code from Nuki, because I cannot login to my Nuki account?

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