Why are my users not populating

[AnnR]

In different areas where I need to set users it is saying no names and when I try to type in the username nothing comes up, this is the same for a number of my team members. 

Please help

[Nic Brough -Adaptavist-]

This sounds like you do not have "browse users" permission.  Log in as an administrator and check that you have the permission - go to Admin > Global Permissions and check the groups who can browse users (unless you have a good reason not to expose the full list of users to everyone, a lot of us simply put "jira-users" in there, so it's global)