Can't find a specific user when trying to assign them a task

Hello all, 

I am facing an issue with assigning a task to a specific user. Whenever the user is searched in the collaborative tasks to assign them a task, the search returns to results. The same when trying to add them to a Dashboard as well. 

However, the user does have all required privileges for the collaborative space, and they can indeed login into the platform, and search for all the content of the platform, like anyone else. 

In the members control center, the user is added and has the required roles and privileges as well. 

Please let me know if anyone has ran across the same issue. 

Note: This is an on premise deployment of the platform for R2022x

Thank you in advance!