Why is a user not available to add to a project team?

Before a user can be added to a team, in Replicon or in Polaris, they must be assigned the Project Resource user type in their User permission set.

Contact your system administrator to have this assigned to your resources.

Related links

Assigning a project team in Replicon
How do I prevent all users from being automatically assigned to new projects?
Why isn't a certain project available in a user's timesheet?
Assigning tasks to team members in Replicon
Setting up a project in Replicon