Hi Jessica,

I assume you are trying to call some MS APIs like "Mail.Send", etc.

To call the APIs without users login, below are the steps required.

• Register an application in MS Azure portal
• You can get the token using the API "https://login.microsoftonline.com/{tenant}/oauth2/v2.0/token"
  https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-auth-code-flow
• In Azure portal, add "Application" level API Permissions for your required APIs, as shown below
  
• Now using the token got using step #2, you can call the APIs without users signed in

Also, have a look at the forge component https://www.outsystems.com/forge/component-overview/7875/ms-graph-connector-oauth-2-0 which has demo module to show this.

Regards,

Karthik