I would start by looking at the Sharing on the tasks that are showing up as grayed out. That indicates to me that the people looking at the task list don't have the proper Sharing permissions to open the tasks and view the information. Check out this article on the Support website about task access:
https://support.workfront.com/hc/en-us/articles/217179507-Task-Access Being part of a Resource Pool or being a Resource Manager doesn't grant any kind of access to tasks. Hierarchy to items is first granted with the License Type (plan or work), then the Access Level, then the permissions on the individual item. Some item-level permissions are granted when assigning a task to a person (these are set at the global system level and on an individual project). When troubleshooting, I always start with the individual item to make sure it's shared with the people who need to access it. That usually solves the problem. I've attached some files that might be helpful in understanding the access hierarchy. Allison Lippert Workfront allisonlippert@workfront.com