@Nerin Peter Chetty (For Azure) ,
I think this is the limitation of language pack.
Unfortunately, as of now Azure AD B2C only supports Alphanumerical characters. I saw similar issue from another customer here.
Currently username must begin with an alphabetical character or number and can only contain alphanumeric characters along the following symbols '_' and '-'.
There is similar request raised in User forum regarding non-alphanumeric characters which you can vote it for future requirement for product team.
Thanks,
Akshay Kaushik
Please "Accept the answer", "Upvote" and share your feedback (Yes/No) if the suggestion works as per your business need. This will help us and others in the community as well.