OutSystems Platform allows configuring multiple "User Providers". This means that, in an environment, multiple user spaces exist, and users with the same information (login name, user name, etc) may exist. You may refer to this article for more information on the topic.
Default user providers
In a standard setup, you will find two distinct user spaces in an OutSystems Platform:
- Application Users (managed under the Users "User Provider"). More on application users.
- IT Users (managed under the ServiceCenter "User Provider"). These are the credentials used in Service Studio, Service Center and LifeTime. More on IT Users.
There is also multi-tenancy: for a given User Provider, multiple "tenants" can exist (this is useful, for example, in SaaS applications). If you have multiple tenants for a given User Provider, each tenant has their own "user space". More on multi-tenancy.
My login works in ServiceCenter but does not work in Users...
If you are having trouble logging in with a given username under Users, but are able to login just fine in ServiceCenter, your problem can be:
- an issue of multi-tenancy (somehow your user from Users got moved to a different tenant)
- your user in the Users provider is inactive
- your user in Users has a different password
- the entry for your Users object in the database has a different password, and you are not resetting it well
- Users is configured for external authentication  and the user does not exist in the external authentication system - so login is not possible.
In the opposite situation (you can login in Users but not in ServiceCenter) you were probably never created as an IT user. In that situation, request that a user is created for you under ServiceCenter / LifeTime.