Hi @Niels1966, welcome to the community.
I reviewed your account and see some verification emails have been sent to you, which might explain why you are unable to sign in. You also have a security email set up on your account so please check it for the most recent verification email (valid for 2 hours). If it has expired already try to sign in again with your master password to trigger a new one.
I've submitted a support ticket for you.