How and why to enable USER PICKER on Cloud

Answer

When you encounter a problem in Tempo views that you can not find other users (e.g., when adding users to teams, viewing the Timesheet of other users) even if you have permission to manage teams or view worklogs of others, it might be caused by the Tempo app not having access to browser users and groups.
This permission is required by add-ons like Tempo to check which permissions a user has in Jira and which groups this user belongs to. This is not a Tempo-specific setting but is used by all apps that need to check on user permissions. 

To give this permission to apps, please navigate to Jira Settings > System > Global Permissions and grant the "Browse Users and Groups" Permission to the “atlassian-addons-admin” Jira Group. This permission is essential for the Tempo plugin to work properly. Lacking this permission may result in misbehavior of apps.