Can't login to IAM Identity Center after setup

Hello, I've setup my access to the IAM Identity Center as documented and I've received the invitation email. Clicking on the button "Accept invitation" in this email, I get the following message:

What's wrong here ? I've tried several times, at several hours intervals, but still doesn't work. However, the connection to the AWS console and to the IAM service works, as well as AWS CLI commands.

Kind regards, Nicolas