When users are added as collaborators to a project, they are unable to open the project.
The user does not have a local posix account on the specific compute node and cannot be given the proper permissions.
Part of the process of adding the local account for each user is to make their own project. This triggers AEN to create a project, create a local posix account on the compute node and assign the ACLs for that account.
Create a new project for each of the affected users, then you can delete this project and re-assign them as collaborators on the original project.
The act of removing them as collaborators and adding them again triggers the scripts that set the ACLs on the project using the newly created posix accounts.