Users are Assigned as Collaborator but Can't see Requisition Information

There are some users who are assigned as Collaborators on a requisition that can see the the requisition and its information. However, there are some users that say they are assigned to Collaborators but unable to see the requisition and its information. The users who said they can't see the requisition information are tied to the Business Unit of the requisition so I'm not sure if it's a security issue, etc.

So I guess I'm asking is there any security or profile needed for someone to fully utilize the Collaborator funcationality?

Thanks!