@Gassim I noticed on play that creating user with spaces is no more allowed
https://play.im.dhis2.org/stable-2-41-1/dhis-web-user/index.html#/users/new

is it possible that this new constraints block the new login page?
So I can confirm the blanks are the problem.
We fixed
update userinfo set username = 'User_Name' where uid= 'viBdNlLjzzv';
restarted the server
then managed to login with the new and the old page.
We have 60 users with blanks
select username from userinfo where username like '% %' ;
Do you plan to migrate every user or remove that “constraint” in the api/41/auth/login enpoint ?
Can you share an sql script to find all the bad usernames ? What is the regexp used ? I guess the problem arrived with 41.x versions (and the new login page) ?
Same problem with accent : Stéphan or Élie were allowed before, not anymore in 41.x