For any team members that were not added to the project via the 'Conversations' section of the project in the New UX, use one of the below options to grant the access to the user:
Option 1: Assign the resource to any task on the project via the New UX. The user will then have access to all the tasks on that specific project.
Option 2: Manually add the access right using the following steps:
1. In the Classic UI, go to Administration->Resources and click on the resource name
2. From the 'Resource's Access Rights' tab drop down, select 'Instance'
3. Click 'Add'
4. For Object, select Project and click 'Next'
5. Check the check box next to 'Project - Task Management' and click 'Add and Continue'
6. Check the check box next to the project the user should have the access for
7. Click 'Add'
Note: To grant this access to multiple projects at the same time, the 'Project - Task Management' access right is not yet available at the global level, but you can grant this level at the OBS level for resources to allow them to have this access to all projects in the same OBS.